an introduction to NMR
HNMR核磁共振
Shown by integral trace.
31 =>
How Many Hydrogens?
When the molecular formula is known, each integral rise can be assigned to a particular nΒιβλιοθήκη mber of hydrogens.
20
Typical Values
=>
21
Poblem 4
Which set of protons in each of the following compounds is the least shielded? Which set of protons in each compound is the most shielded?
H3C
Si CH3
=>
16
Chemical Shift
Measured in parts per million. Ratio of shift downfield from TMS (Hz) to total spectrometer frequency (Hz). Same value for 60, 100, or 300 MHz machine. Called the delta scale.
=>
19
Location of Signals
More electronegative atoms deshield more and give larger shift values. Effect decreases with distance. CH3CH2CH2Cl Additional electronegative atoms cause increase in chemical shift. =>
Introduction_to_MetaboAnalystR
MetaboAnalystR reads in both comma separated values (CSV) and text (txt) files. The package also accepts zipped files (.zip), including NMR peak, MS peak, and LC/GC-MS spectra (NetCDF, mzDATA, mzXML) data. We will first begin with an example dataset downloadable from the MetaboAnalyst web-server called "cachexia_concentrations.csv". To begin the analysis, we first have to create an object for data processing, using the function InitDataObjects, and then we will read in the data file using the function Read.TextData. The InitDataObjects is the first function executed when uploading a dataset. It constructs the dataSet object, which is an R list with several variables assigned to it, including the type of data, the data format, and whether or not the data is paired. Is also creates the analSet object, and the imgSet object, which are also lists that will be filled in downstream analysis. Further, the function creates three libraries and databases which will be filled if necessary. Finally, it creates msg.vec, which is a character vector that will contain messages produced from the analysis. It it necessary for users to specify the dataType , (list, conc, specbin, pktable, nmrpeak, mspeak, msspec), and the type of analysis to be performed on the uploaded dataset, analType (stat, pathora, pathqea, msetora, msetssp, msetqea, ts, cmpdmap, smpmap). In this case, we are uploading a compound concentration dataset ("conc"), and will be performing statistical analysis on the dataset ("stat").
NMR relaxometry as a versatile tool to study Li ion dynamics in potential battery materials
article info
Available online 9 February 2012
Keywords: Li ion dynamics NMR spin–lattice relaxation Battery materials Li7La3Zr2O12 Li12Si7
abstract
NMR spin relaxometry is known to be a powerful tool for the investigation of Li þ dynamics in (nonparamagnetic) crystalline and amorphous solids. As long as significant structural changes are absent in a relatively wide temperature range, with NMR spin–lattice (as well as spin–spin) relaxation measurements information on Li self-diffusion parameters such as jump rates and activation energies are accessible. Diffusion-induced NMR relaxation rates are governed by a motional correlation function describing the ion dynamics present. Besides the mean correlation rate of the dynamic process, the motional correlation function (i) reflects deviations from random motion (so-called correlation effects) and (ii) gives insights into the dimensionality of the hopping process. In favorable cases, i.e., when temperature- and frequency-dependent NMR relaxation rates are available over a large dynamic range, NMR spin relaxometry is able to provide a comprehensive picture of the relevant Li dynamic processes. In the present contribution, we exemplarily present two recent variable-temperature 7Li NMR spin– lattice relaxation studies focussing on Liþ dynamics in crystalline ion conductors which are of relevance for battery applications, viz. Li7 La3Zr2O12 and Li12Si7.
NMR中常用的英文缩写和中文名称
NMR中常用的英文缩写和中文名称APT：Attached Proton Test 质子连接实验ASIS：Aromatic Solvent Induced Shift 芳香溶剂诱导位移BBDR：Broad Band Double Resonance 宽带双共振BIRD：Bilinear Rotation Decoupling 双线性旋转去偶（脉冲）COLOC：Correlated Spectroscopy for Long Range Coupling 远程偶合相关谱COSY：( Homonuclear chemical shift ) COrrelation SpectroscopY （同核化学位移）相关谱CP：Cross Polarization 交叉极化CP/MAS：Cross Polarization / Magic Angle Spinning 交叉极化魔角自旋CSA：Chemical Shift Anisotropy 化学位移各向异性CSCM：Chemical Shift Correlation Map 化学位移相关图CW：continuous wave 连续波DD：Dipole-Dipole 偶极-偶极DECSY：Double-quantum Echo Correlated Spectroscopy 双量子回波相关谱DEPT：Distortionless Enhancement by Polarization Transfer 无畸变极化转移增强2DFTS：two Dimensional FT Spectroscopy 二维傅立叶变换谱DNMR：Dynamic NMR 动态NMRDNP：Dynamic Nuclear Polarization 动态核极化DQ(C)：Double Quantum (Coherence) 双量子（相干）DQD ：Digital Quadrature Detection 数字正交检测DQF：Double Quantum Filter 双量子滤波DQF-COSY：Double Quantum Filtered COSY 双量子滤波COSYDRDS：Double Resonance Difference Spectroscopy 双共振差谱EXSY：Exchange Spectroscopy 交换谱INADEQUATE：Incredible Natural Abundance Double Quantum Transfer Experiment 稀核双量子转移实验（简称双量子实验，或双量子谱）INDOR：Internuclear Double Resonance 核间双共振INEPT：Insensitive Nuclei Enhanced by Polarization 非灵敏核极化转移增强INVERSE：H,X correlation via 1H detection 检测1H的H,X核相关IR：Inversion-Recovery 反（翻）转回复JRES：J-resolved spectroscopy J-分解谱LIS ：Lanthanide (chemical shift reagent ) Induced Shift 镧系（化学位移试剂）诱导位移LSR：Lanthanide Shift Reagent 镧系位移试剂MAS：Magic-Angle Spinning 魔角自旋MQ(C)：Multiple-Quantum ( Coherence ) 多量子（相干）MQF：Multiple-Quantum Filter 多量子滤波MQMAS：Multiple-Quantum Magic-Angle Spinning 多量子魔角自旋MQS：Multi Quantum Spectroscopy 多量子谱NMR：Nuclear Magnetic Resonance 核磁共振NOE：Nuclear Overhauser Effect 核Overhauser效应（NOE）NOESY：Nuclear Overhauser Effect Spectroscopy 二维NOE谱NQR：Nuclear Quadrupole Resonance 核四极共振PFG：Pulsed Gradient Field 脉冲梯度场PGSE：Pulsed Gradient Spin Echo 脉冲梯度自旋回波PRFT：Partially Relaxed Fourier Transform 部分弛豫傅立叶变换PSD：Phase-sensitive Detection 相敏检测PW：Pulse Width 脉宽RCT：Relayed Coherence Transfer 接力相干转移RECSY：Multistep Relayed Coherence Spectroscopy 多步接力相干谱REDOR：Rotational Echo Double Resonance 旋转回波双共振RELAY：Relayed Correlation Spectroscopy 接力相关谱RF：Radio Frequency 射频ROESY：Rotating Frame Overhauser Effect Spectroscopy 旋转坐标系NOE谱ROTO：ROESY-TOCSY Relay ROESY-TOCSY 接力谱SC：Scalar Coupling 标量偶合SDDS：Spin Decoupling Difference Spectroscopy 自旋去偶差谱SE：Spin Echo 自旋回波SECSY：Spin-Echo Correlated Spectroscopy自旋回波相关谱SEDOR：Spin Echo Double Resonance 自旋回波双共振SEFT：Spin-Echo Fourier Transform Spectroscopy (with J modulation) （J-调制）自旋回波傅立叶变换谱SELINCOR：Selective Inverse Correlation 选择性反相关SELINQUATE：Selective INADEQUA TE 选择性双量子（实验）SFORD：Single Frequency Off-Resonance Decoupling 单频偏共振去偶SNR or S/N：Signal-to-noise Ratio 信/ 燥比SQF：Single-Quantum Filter 单量子滤波SR：Saturation-Recovery 饱和恢复TCF：Time Correlation Function 时间相关涵数TOCSY：Total Correlation Spectroscopy 全（总）相关谱TORO：TOCSY-ROESY Relay TOCSY-ROESY接力TQF：Triple-Quantum Filter 三量子滤波WALTZ-16：A broadband decoupling sequence 宽带去偶序列WATERGATE：Water suppression pulse sequence 水峰压制脉冲序列WEFT：Water Eliminated Fourier Transform 水峰消除傅立叶变换ZQ(C)：Zero-Quantum (Coherence) 零量子相干ZQF：Zero-Quantum Filter 零量子滤波T1：Longitudinal (spin-lattice) relaxation time for MZ 纵向（自旋-晶格）弛豫时间T2：Transverse (spin-spin) relaxation time for Mxy 横向（自旋-自旋）弛豫时间tm：mixing time 混合时间rc：rotational correlation time 旋转相关时间。
NMRPipe and nmrDraw processing and visualizing 2D data
NmrPipe and nmrDraw: Processing and visualizing 2D data.See 'Introduction to nmrPipe' for basic program description.NmrPipe is really designed for multidimensional NMR processing; i.e. Executing repetitive operations on many FIDs. As described in the introductory laboratory for 1D data, the nD data is first converted from the spectrometer format to an nmrPipe format, then a processing script is created to fourier transform the dataset. Visualization can be done immediately with nmrDraw, or the processed data can be transported to other programs ( NMRView and Sparky for example).We will examine two different 2D datasets and their conversion and processing scripts. Next week we will continue with more data analysis tools, and examine a 3D dataset conversion and processing script.Dataset #1. 2D Absolute-value or magnitude-mode COSY; 'cosy.fid'Dataset #2. 2D phase-sensitive 'echo-antiecho' or 'Rance-Kay' C13-HSQC; 'hsqc.fid' Dataset #3. 2D phase-sensitive 'States' proton-proton TOCSY; 'tocsy.fid'Copy the datasets into your nmrPipe directory ( see instructions in class).Dataset 1. Absolute-value or magnitude-mode COSY.Name: cosy.fidThe dataset collected on a Varian used the 'gCOSY' experiment,which is a gradient version of the traditional phase-cycled COSY, however the data is treated in the same way. This is not a phase-sensitive experiment, and so the data is usually displayed in absolute value mode after application of sinebell window functions to improve the poor lineshape.1.1 Convert dataset using 'varian' tcl scripta) cd your_nmrpipe_directory/cosy.fid, type 'varian'b) click 'read parameters' ; now have x (t2 direct dimension) and y-axis (t1 or indirect dimension.- Some of these values are incorrect and must be changed.Total Points R+I: 256Acquisition Mode: RealObserve Freq Mhz: 499.641e) Save the script, execute the script, then quit.Lets examine the '' script that was generated. If you are not inyour_nmrpipe_directory/cosy.fid directory, go there now and look at the script using an editor, or type 'more '.---------------------------------------------------#!/bin/cshvar2pipe -in ./fid -noaswap \-xN 2048 -yN 256 \-xT 1024 -yT 256 \-xMODE Complex -yMODE Real \-xSW 3869.969 -ySW 3869.969 \-xOBS 499.641 -yOBS 499.641 \-xCAR 4.773 -yCAR 4.773 \-xLAB H1 -yLAB H1 \-ndim 2 -aq2D Magnitude \-out ./test.fid -verb -ovsleep 5-------------------------------------------------------We now have two dimensions and two axes, designated as x and y. The x dimension is the direct dimension and is always collected as complex data ( quadrature detection). Thus the xMODE is complex, and the xN ( real + imaginary points) parameter , i.e. the number of FIDs, is twice the xT (complex points) parameter, i.e. the number of sampled dwell times.The indirect y-axis is being read as 'Real' data. Here the number of FIDs, yN, is equal to the number of increments, yT. The data is also being processed as magnitude mode data ( -aq2D parameter). This is particular to magnitude COSY data only.The last line writes the output to 'test.fid' ( -ov = overwrites old data ) with some screen messages (-verb).Note that you can specify the ppm reference of the center of each axis (xCAR, yCAR) if this is known. These values can be changed later.1.2 Process the 2D COSYWe will use the 'macro' writing tool of nmrDraw as discussed in the previous introduction lab.a) Change directory ('cd') to your nmrpipe-directory/cosy.fid directory.b) type nmrDraw & to bring up the program window ( see introduction)c) pull down File menu to 'macro edit' or just type 'm' to get new window.d) pulldown 'Process 2D' menu and select 'Basic 2D'e) Edit it to look like this: ( comments at right indicate changes, don't include them). The MC function can be added from Transforms – Modulus;The REV function can be added from Transforms – Reverse;The TP function can be added from Transforms – Transpose.Make sure there are no empty lines, or spaces after the backslash ' \' .#!/bin/cshnmrPipe -in test.fid \| nmrPipe -fn SP -off 0.0 -end 1.00 -pow 1 -c 1.0 \ ## change SP -off 0.0| nmrPipe -fn ZF -auto \ ## standard zero fill| nmrPipe -fn FT -auto \ ## complex ft## deleted line with PS (phase) function.| nmrPipe -fn TP \| nmrPipe -fn SP -off 0.0 -end 1.00 -pow 1 -c 1.0 \ ## change SP -off 0.0| nmrPipe -fn ZF -auto \| nmrPipe -fn FT -auto \## deleted line with PS function.| nmrPipe -fn MC \ ## added MC function; gives abs val display. | nmrPipe -fn REV -di -verb \ ## added REVerse function to flip y-axis.| nmrPipe -fn TP \ ## added TP, puts f2 axis back on x-axis-ov -out test.ft2f) Save, then Execute, then Done.1.3 Displaying 2D COSY spectrum.a) You should still be inside the cosy.fid directory. Pull down ( right button) File menu and select file. Highlight 'test.ft2' and click 'Read/Draw', then Done.typing 'd' (or Draw menu -Contours)d) exit from the zoom mode with 'e' ( or Mouse menu - Exit mode.)e) you can return to the full display by typing 'f' ( or Draw menu – 2D Full)1.4 Using the 2D Display1.4.1 Referencinga) Zoom into a region.b) Display crosshairs by typing 'b' ( or Mouse menu -1D Both).c) Place on a peak and type 'C' ('shift c' ) ( or File menu – Calibrate axis)d) choose axis, and change the 'New ppm Value'e) Click Apply; for permanent change, click Save.f) Repeat with other axis.1.4.2 Getting peak positions.a) Zoom into a region of peaks. Exit zoom mode.b) Type 'l' ( or Mouse menu- 2D Location). The holding down left button gives the location of the cursor in points and ppm, as well as the height of the peak at that position.1.4.3 Plotting a specific region.a) Type 'L' ( shift-l) to bring up a small window that allows entry of axis limits. The default units are points, but you can pull down the units list and select ppm. Enter the limits, e.g. 5.5 , 3.0 for both Horiz. and Vert., then 'Draw', and 'Done'.b) Type 'P' ( or File menu-Hard copy plot) to bring up the plotting window. Execute will create a postscript plot file named nmrDraw.ps in the current directory. This can be sent to a printer or further manipulated in a drawing program.2. Dataset #2: phase-sensitive HSQC.This dataset is called 'hsqc.fid' and is a gradient HSQC experiment, where the frequency discrimination and phase-sensitive results are obtained by the 'echo-antiecho' or 'Rance-Kay' method of data collection.For simplicity, quit the nmrDraw program, and we'll restart it later.2.1 HSQC data Conversion.The same protocol is used as for the COSY described above.Change directory to hsqc.fid directory, and type 'varian'. The only change to the conversion script is to make the yMODE parameter Rance-Kay ( or echo-antiecho) rather than complex. This mode invokes a shuffling of data, and the final converted data can now be processed with a standard 'States' phase-sensitive processing macro.---------------------------------------------------#!/bin/cshvar2pipe -in ./fid -noaswap \-xN 1394 -yN 128 \-xT 697 -yT 64 \-xMODE Complex -yMODE Rance-Kay \ ## Note the change in yMODE-xSW 3869.969 -ySW 20100.503 \-xOBS 499.641 -yOBS 125.644 \-xCAR 4.773 -yCAR 82.861 \-xLAB H1 -yLAB C13 \-ndim 2 -aq2D States \-out ./test.fid -verb -ovsleep 5-----------------------------------------------------Note that the -yN parameter is twice the -yT parameter, indicating that we are collecting two datasets to allow for 'quadrature' in the indirect dimension. Also the y axis now correctly has the C13 ( decoupler) parameters.2.2 HSQC dataset processingThis processing macro is quite different than the COSY macro, so we will use the macro edit command and write it from scratch. Since it is phase-sensitive data, we will have to 'phase' the data.a) Start nmrDraw from the hsqc.fid directory.b) File menu-select file – read and draw the raw dataset, test.fid.c) Type 'h' ( Mouse menu – 1D horizontal). Bring the horizontal line down to the bottom, so that it is showing FID #1 – the Y: point should be 1.d) Autoprocess the 1D (Proc menu).e) turn on phasing, and phase spectrum with P0. Note the value of PO ( e.g. -136). Type 'e' to escape from the horizontal display.If S/N is too low, ignore the phasing step. You can always adjust phasing later.2.2 HSQC dataset processing cont'd.f) Type 'm' to open macro editor, and select Basic 2D from the Process 2D menu.g) edit the first PS function line so the value of -p0 is -136.Also add lines at the end to REVerse the y axis, then to transpose so H1 is on x-axis.------------------------------------------------------------------#!/bin/cshnmrPipe -in test.fid \| nmrPipe -fn SP -off 0.5 -end 1.00 -pow 1 -c 1.0 \ ## SP -off 0.5 is Cosine window. | nmrPipe -fn ZF -auto \| nmrPipe -fn FT -auto \| nmrPipe -fn PS -p0 -136.00 -p1 0.00 -di -verb \ ## Change -p0 value| nmrPipe -fn TP \| nmrPipe -fn SP -off 0.5 -end 1.00 -pow 1 -c 1.0 \| nmrPipe -fn ZF -auto \| nmrPipe -fn FT -auto \| nmrPipe -fn PS -p0 0.00 -p1 0.00 -di -verb \ ## see below| nmrPipe -fn REV \ ## Add REV function| nmrPipe -fn TP \ ## Add TP function-ov -out test.ft2------------------------------------------------------------------------h) Save and Execute.i) Display the spectrum by selecting test.ft2 . Note that the phase along the y-axis is wrong.j) Zoom if necessary, and display the vertical cursor by typing 'v' ( or Mouse menu-1D vertical) and place it over a peak. Make sure the phasing is on and adjust p0. Note the value ( e.g. -94). Exit cursor mode by typing 'e'.k) return to the macro editor and change the second PS function line so p0 is 94, i.e. negative of the recorded value ( due to TP and REV functions). Save and execute. Re-read and display test.ft2 – it should look like this:2.2 HSQC dataset processing cont'd.For nD data where the indirect dimension(s) is collected with few points, it is often advantageous to increase the number of points and digital resolution by 'Linear Prediction'. This calculation determines the frequency and decay rate of the peaks in an FID or interferrogram, and extends them mathematically. It is very useful for spectra like 2D HSQC, where experimental time is needed to improve signal-to-noise, so the number of increments is limited.a) Edit the file, and add the Linear Prediction function in the second dimension.------------------------------------------------------------------#!/bin/cshnmrPipe -in test.fid \| nmrPipe -fn SP -off 0.5 -end 1.00 -pow 1 -c 1.0 \| nmrPipe -fn ZF -auto \| nmrPipe -fn FT -auto \| nmrPipe -fn PS -p0 -136.00 -p1 0.00 -di -verb \| nmrPipe -fn TP \| nmrPipe -fn SP -off 0.5 -end 1.00 -pow 1 -c 1.0 \| nmrPipe -fn LP -fb \ ## Add LP function here ##| nmrPipe -fn ZF -auto \| nmrPipe -fn FT -auto \| nmrPipe -fn PS -p0 94.00 -p1 0.00 -di -verb \| nmrPipe -fn REV \| nmrPipe -fn TP \-ov -out test.ft2------------------------------------------------------------------------b) Rerun the new macro and see the result – notice it takes a lot longer to process.Without Linear Prediction.With Linear Prediction.2.3 HSQC dataset analysis2.3.1 Referencing.The chemical shift axes are not correct, since we used the default values in the conversion script. The peak at the left ( see plot above) is chloroform and we can use it to reference the spectrum.a) zoom around the chloroform peak area by typing 'z' ,adjusting box dimensions, followed by right click. Type 'e' to exit zoom mode.a) type 'b' to get crosshairs ( vertical and horizontal cursors), place on peakb) type 'C' to get calibration box, choose x, and enter 7.24, then Apply. Choose y, enter77.0, Apply, then Save, then Done.c) exit crosshair mode with 'e', and type 'f' to get full spectrum.The spectrum should now be referenced correctly, and any redisplay will give the updated values. However, the original data still retains the wrong values, and reprocessing will give the old values. To permanently correct these values, you must edit the file and change xCAR and yCAR. The spectrum is 2048 points along x and 128 points along y. Therefore, the ppm values at 1024 and 64 points for x and y respectively, will be the correct xCAR and yCAR values. Then rerun the script and the converted data will now reflect the new referencing values.2.3.2 Automatic peak pickinga) zoom around a few peaks. ( e.g. 4.3 to 5.4, 63 to 77)b) Pull down Peak menu, select Peak Detection. This will bring up a box.c) Click on Clear, then Detect, then Done.The spectrum should show number labels on each peak, and a text file called 'test.tab' is created in the current directory. You can examine this file, which contains all the information about peak positions, peak heights, and peak volumes.Exercise: 2D phase-sensitive ( 'States') TOCSY datasetConvert and process the 'tocsy.fid' dataset. It is a H1-H1 correlated, phase-sensitive experiment; that is collected with quadrature in f1 and the data is complex in both dimensions. You will have to edit the conversion macro so that x and y axes are both H1. The processing macro will be a standard 2D macro; cosine-bell window functions are appropriate, and both dimensions will have to be phased. Linear prediction is not necessary.。
NMR-intro
such that it is an integral or half integral of h (Plank constant)
m is the magnetic or directional quantum number it can take values: m = I , I-1 , …. , -I B0 Pz = + ½ h Pz = - ½ h
a b
m=+½
m=-½
There are then 2I + 1 orientations in the field
Directional Quantization
The Magnetic Moment m = m g h precess around the z-axis (magnetic field B0) nL = g B0/2p B0 Pz = + ½ h Pz = - ½ h
a b
m=+½ m=-½
The Energy of a magnetic dipole in the magnetic field B0 is: E = - m B0 Where m = m g h
For a nuclei with (2I+1) orientations the energy of the individual states (Zeeman levels) is: E = - m g h B0
Additional Elements in Organic Chemistry • • • • • Halogens: 19F, Cl, Br, I 31P, S B, 29Si Na Co, Cd, W, Pt, Hg…
1D NMR : Pulse ->FID Acquisition -> Fourier Transform
中英文核磁说明书
中英文核磁说明书Nuclear Magnetic Resonance (NMR) Instructions核磁共振（NMR）说明书1. Introduction: The nuclear magnetic resonance (NMR) technique is widely used in chemistry, physics, and biology for studying the structure, dynamics, and interactions of molecules. This instruction manual provides essential information on how to properly operate an NMR instrument.1. 简介：核磁共振（NMR）技术广泛应用于化学、物理和生物学等领域，用于研究分子的结构、动力学和相互作用。
本说明书提供了正确操作核磁共振仪器的基本信息。
2. Safety precautions: It is crucial to follow safety precautions while working with NMR instruments. This includes wearing appropriate personal protective equipment, ensuring proper ventilation, and maintaining a safe working environment.2. 安全注意事项：使用核磁共振仪器时，必须遵循安全注意事项。
包括穿戴适当的个人防护装备，确保良好通风和维持安全工作环境。
3. Instrument setup: Proper instrument setup is important for obtaining accurate NMR data. This includes calibrating the instrument, optimizing the magnetic field, and ensuring that all necessary components are properly connected.3. 仪器设置：正确的仪器设置对于获取准确的核磁共振数据至关重要。
赝势的介绍
Vl(r)|l l|.
Traditionally PPs are split into a local part, long-ranged and behaving like −Zv e2/r for r → ∞, and a short-ranged semilocal term: ˆ ps = V ˆloc + V ˆSL, V ˆloc ≡ Vloc(r), V ˆSL ≡ V
2 d −2π (rφ(r)) d
d ln φ(r) dr
rc
= 4π
rc 0
|φ(r)|2r2dr
valid for any regular solution of the Schr¨ odinger equation at energy . – non local: there is one potential per angular momentum: V ps(r) =
ps 2 fl|φps l (r )| l
(fl is the occupancy of state with angular momentum l).
Desirable characteristics of a Pseudopotential: • Transferability: can be estimated from atomic calculations on different configurations. In many cases simple unscreening produces an unacceptable loss of transferability. May require the nonlinear core correction: Vlps(r) = Vl(r) − VH (nps(r)) − Vxc(nc(r) + nps(r)) where nc(r) is the core charge of the atom (Froyen, Louie, Cohen 1982) • Softness: atoms with strongly oscillating pseudo-wavefunctions (first-row elements, elements with 3d and 4f valence electrons) will produce hard PPs requiring many PWs in calculations. Larger core radius means better softness but worse transferability. Various recipes to get optimal smoothness without compromising transferability: Troullier and Martins (1990), Rappe Rabe Kaxiras Joannopoulos (1990)
布鲁克核磁Xwinnmr一维氢谱操作步骤
CHM/MCMP 616 Principles and Practice of modern 1Dand2D NMR SPECTROSCOPYOptimized 1D SpectraandGradient ShimmingBrukerLAB EXERCISE ILast revised:June 12, 2002 (3:02pm)CHM/MCMP 616Bruker Lab1 Optimized 1D Spectra &Gradient ShimmingPage2WARNINGAll the magnets in the NMR facility are fitted with pneumatic anti-vibration platforms or legs. The magnets can be easily damaged whilst the anti-vibration system is engaged.NEVER lean against the Magnet or the anti-vibration system.NEVER hold or pull any part of the Magnet or anti-vibration system.NEVER stand on the Anti-Vibration system whilst it is engagedSAFETY PROCEDURESFor your safety obey all notices posted in the NMR facility and especially in the vicinity of the Magnets.DO NOT take metal objects within the 5 Gauss field lineDO NOT allow unauthorized individuals to approach the MagnetMAGNET QUENCHIn case of a Magnet quench, leave the area in a calm and orderly fashion.If the room fills with escaping gases kneel down and crawl along the floor. The oxygen level will be higher here and visibility will be better.I.OBJECTIVES (6)II.INTRODUCTION (6)III.LOGGING ON TO THE SPECTROMETER (6)A.STARTING A NEW SESSION (6)B.LOGGING OUT FROM A PREVIOUS SESSION (6)C.LOGGING INTO A NEW SESSION (7)YOUT OF XWINNMR WINDOWS (8)ANIZATION OF XWINNMR (8)A.INTRODUCTION (8)B.XWINNMR FILE SYSTEM (9)ER FILES (11)1.DATA DIRECTORIES (11)VI.SAMPLE PREPARATION, SAMPLES VOLUME AND DEPTH GAUGE (11)A.SAMPLE PREPARATION (11)B.SAMPLE INSERTION (11)VII.LOCK SIGNAL ADJUSTMENT (13)A.SEMI AUTOMATIC (DRX500'S/ ARX) (13)B.FROM AUTOLOCK TO MANUAL LOCK (14)MANDS, MACROS & PARAMETERS (refer to XWINNMR Software Manuals) (16)MANDS AND MACROS (16)B.PARAMETERS (17)C.SPECIAL COMMANDS (18)D.INITIALIZING A NEW EXPERIMENT (18)E.SAVING AND RETRIEVING YOUR DATA (18)IX.SAMPLE VOLUME AND DEPTH (18)X.SPECTROMETER HARDWARE LAYOUT (19)A.MAGNET (20)B.PROBE (20)C.LOCK CIRCUIT (20)D.TRANSMITTER CIRCUIT (22)E.DETECTOR CIRCUIT (22)F.DECOUPLER CIRCUIT (22)G.GRADIENT AMPLIFIER (NOT SHOWN) (22)XI.TUNING PROBES ON THE DRX (22)A.WHY TUNE THE PROBE? (22)B.PROBE TUNING COMMANDS (23)C.SAMPLE CHANGES (23)A.QUARTER-WAVELENGTH CABLE (1/48) (23)B.GRAPHICAL TUNING INTERFACE “WOBB (23)XII.GRADIENT SHIMMING (24)A.GRADIENT SHIMMING METHOD (25)B.GRADIENT SHIMMING COMMANDS AND PARAMETERS (25)C.HOW DOES GRADIENT SHIMMING WORK? (25)D.GRADIENT SHIM MAP CREATION (26)E.STARTING GRADIENT SHIMMING (26)DISPLAYING THE SHIMMAP (27)XIII.SETTING UP AN ARRAY (28)A.PREPARATION (28)B.SET O1 AND SW (29)C.DEFINE PHASE CORRECTION AND PLOT REGION (29)D.PULSE WIDTH ARRAY (30)XIV.DATA PROCESSING (31)A.INTRODUCTION (31)B.ENHANCEMENT FUNCTIONS (31)C.OTHER TYPES OF ENHANCEMENT FUNCTIONS (32)D.HOW TO APPLY WINDOW FUNCTIONS (33)E.APPLICATION OF WINDOW FUNCTIONS IN 2D AND 3D NMR (34)F.LINEAR PREDICTION AND MAXIMUM ENTROPY METHODS (34)G.APPLICATION OF LP TO 1D NMR (34)XV.REFERENCES (35)XVI.HOMEWORK (36)A.PULSE CALIBRATION (36)B.GRADIENT SHIMMING (36)C.WINDOW FUNCTIONS (36)D.SAMPLE PREPARATION (36)E.HARDWARE COMPONENTS (37)F.ARRAY (37)G.WEB PAGE QUESTION (37)I.OBJECTIVESThe purpose of this laboratory is to review some basic NMR techniques for the optimum acquisition of 1D spectra. The following procedures will be reviewed: tuning, locking, spectral width and transmitter offset optimization. The laboratory will also demonstrate proper techniques for pulse width optimization. We will introduce the student to the techniques of gradient shimming. It will be shown how to find a proton or deuterium shim map and how use this map to obtain good quality spectra with a minimum of shimming by hand. In addition a description of the spectrometer hardware is given and the capabilities of the Purdue Interdepartmental NMR Facility (PINMRF) will be reviewed. Finally, some important aspects of data-processing are discussed such as the use of window functions for the enhancement of signal to noise or resolution and improvement of spectra through back prediction of the first few distorted data points or forward prediction of a large number of additional points.II.INTRODUCTIONThe quality of an NMR spectrum is dependent on the stability of a number of factors in the surroundings of the spectrometer. These factors have been optimized for you before you begin to acquire data. Room temperature is strictly controlled. The influence of building vibrations has been minimized by placing the magnet on vibration dampers. The room (and the adjacent space) where the NMR spectrometer and its magnet are located have been screened for any large ferromagnetic objects that may seriously perturb the static magnetic field. In addition, the sample temperature is also regulated by means of a variable temperature unit that uses dry air or nitrogen gas. Finally, it is up to the user to assure that the spectrum is collected under optimum conditions.III.LOGGING ON TO THE SPECTROMETERA.STARTING A NEW SESSION1.Each user must sign-in and enter the information into the billing logbook.2.The user must then sign-in to the operators log book.3.After completing these 2 sign-in’s, the NMR user may enter the log-in ID andpassword at the host computer.B.LOGGING OUT FROM A PREVIOUS SESSION-When you first arrive to use the machine:1.Check for any messages from previous users.-They may have left a note asking you to save their data for them.2.If the screen is locked you must contact the user or contact one of the NMRstaff members.3. If there are no messages, check which group is using the machine.-Do this by typing "whoami" in one of the shell windows.4.If necessary log out from the previous user's XWINNMR session by typingexit. To log out of UNIX, hold down the right mouse button at the desktopand select LOGOUT from the bottom of the menu.C.LOGGING INTO A NEW SESSION-Initially, the monitor screen of the host computer may be dark. This is due to the screen saver function. To activate the display, move the mouse. If the screen remains dark after moving the mouse, make certain that the monitor power is on. When the spectrometer or workstation is not in use, a full Welcome to Machine name screen will appear.1.Type the log-in ID and password into this window (use the account nameand passwd provided to you in class). The log-in ID will appear in thewindow as it is typed in from the keyboard. The password will not bedisplayed when it is entered from the keyboard.2.Once you are logged in, a desktop will appear. Open a UNIX shell window bygoing to the menu option labeled DESKTOP>UNIX SHELL. The prompt willcontain the machine name. e.g.: arx300> or drx500>.3.The XWINNMR program can be launched by typing:arx300>xwinnmr [RETURN]ordrx500>xwinnmr [RETURN] Figure 1.YOUT OF XWINNMR WINDOWSXWINNMR will recall the user’s last data set used in the previous session on the spectrometer. First time users will see a data set labeled PROTON 1 1 and a 1H survey spectrum will appear on the screen. The screen containing the XWINNMR command window and the spectrum will be similar to what is shown below in Figure 2.Figure 2. Layout ofXWINNMR WINDOWANIZATION OF XWINNMRA.INTRODUCTION-Data are organized in sub-directories such as user-directories, experiments, and processes. On the screen, you will find a small window similar to the one shown here. The disk drive name is u, and the user name is the log-in name. In this example, PROTON 1 1 is the data set name. The first of the two numbers is the experiment number and the last number is the process number. So this user is operating in the space labeled PROTON. Within the PROTON data file the acquisition parameters are in experiment 1 and process 1.B.XWINNMR FILE SYSTEMThe main files running XWINNMR are located in the directory /u. Files in this and many other directories cannot be modified by regular users as they contain important configuration parameters that are essential to run the machine. The important files and subdirectories in the directory /u are (note their pathnames are relative to /u) shown below.Figure 3 File Structure of the XWINNMR Program/exp/stan/nmr/par This directory contains sets of standard parameters that are used to set up the standard NMR experiments./u/exp/stan/nmr/lists/pp Every NMR experiment, no matter how simple is controlled by a "pulse-sequence". This is a command file that consists of a series of delays and pulses which are sent to the acquisition computer. Many commonly used standard pulse sequences are alreadyprovided by the manufacturer and are included in this directory. All the files in this directory are text files and they do not control the spectrometer directly. This is done by the compiled versions./exp/stan/nmr/wave Most pulses in NMR experiments are rectangular "hard" pulses. That is they excite the complete region of interest. More and more sequences require the selective excitation of limited regions of the spectrum. This is achieved by using "shaped" pulses. A shaped pulse is a pulse that has had its amplitude and/or phase modified by some mathematical function. The simplest and most often used selective pulse has a gaussian shape./u/conf/instr/autoshim/refmaps It contains shim map files for the different probes. They can be accessed via the gradshim menu./u/exp/stan/nmr/au/src AU programs can be considered as user defined XWINNMRcommands. Anyrepetitive task is most effectively accomplished through an AU program. All commands that can be entered on the XWINNMR command line can also be entered in an AU program in the form of macros. This includes selecting and changing datasets, reading and setting parameters, starting acquisitions, processing data and plotting the result. A simple AU program is nothing else than a sequence of such macros which execute the corresponding XWINNMR commands. However, AU programs may also contain C-language statements. In fact, an AU program is a C-program because all AU macros are translated to C-statements. XWINNMR automatically compiles AU programs to executable binaries, using a C-compiler. XWINNMR offers two other ways of creating user defined commands: XWINNMR macros (not to be confused with AU macros) and Tcl/Tk scripts. They differ from AU programs in that they do not need to be compiled./u/conf/instr/probeheads Files containing specific probe information like pulse widths, powerlevels, shim maps and shim files are stored in this directory./u/conf/instr/spect Spectrometer specific configuration files./prog Contains directories with executable files that are commands used in running a program, for example, “paropt”. Most of these commands in /prog are entered directly by the user. /exp/stan/nmr/lists/mac Macros are files that execute a series of commands in a specified order. For example, when a user types “h” in the Command window this executes a macro called "humpcal".ER FILESUnlike in other nmr software all users share a common directory for macros, pulse sequences, au programs, shim files, tables etc. Users must label files by extending the filenamewith a period followed by their initials (e.g., filename.er). Not doing so will create confusion to other users as system files are in those directories as well.1.DATA DIRECTORIESUsers will store files in their own data directory /u/data/user name. Users have read and write privileges only in their own data directory, however, a user may read other directories.VI.SAMPLE PREPARATION, SAMPLES VOLUME AND DEPTH GAUGEA.SAMPLE PREPARATIONThe method of sample preparation can have a significant impact on the quality of its NMR spectrum. The following is a brief list of suggestions to ensure high sample quality.1.Always use clean and dry sample tubes to avoid contaminating the sample.2.Always use good to high quality sample tubes to avoid unnecessarydifficulties in shimming.3.Filter the sample solution when necessary.4.Always use the same sample volume or solution height and center thesample around the RF coil. This minimizes the shimming that needs to bedone between sample changes.5.Check that the sample tube is held tightly in the spinner so that it does notslip during an experiment.6.Wipe the sample tube clean before inserting it into the depth Gauge.7.For experiments using sample spinning, be sure the spinner, especially thereflectors, is clean. This is important so that the correct spinning rate can bemaintained.8.B.SAMPLE INSERTIONField homogeneity and field to frequency lock are very sensitive to changes in conditions near the magnet. Metal objects near the magnet and vibrations will affect the quality of the NMR spectrum. Once the sample has been inserted into the probe, any activity within the 5 gauss area of the magnet should be avoided.The BSMS/BSCM control panel is used extensively to change samples, to lock and to shim. An illustration of the BSMS keypad is provided in Figure 4.1. Each key on the panel contains a light emitting diode or LED. These lights serve as indicators for each of the functions. If the light is off, the key or function has not been selected. If the light is on, the key or function is selected and it is operating correctly. If the light is blinking, the function is either changing or it is out of regulation.Figure 5. BSMS “BRUKER SMARTS MAGNET CONTROL SYSTEM”. This device can also be controlled from the computer by typing the command bsmsdispPrior to using the BSMS unit make certain that the LOCK or AUTO LOCK and SPIN lights are illuminated.1.Remove the orange/black cap from the upper barrel on top of the magnet. On the BSMS/BSCM press the keys in the following order:LOCK Pressing this key will turn-off the Field Lock for the sample in theprobe or AUTOLOCKSPIN Press the SPIN key to turn-off the Spin Air flow if the diode in theSPIN key is lighted.2nd(ARX only) This is a “SHIFT” or “ALT” key that allows access to thealternate function set. The alternate function (such as LIFT) is listeddirectly below the key.LIFT The LIFT function (listed on the panel--not on the key) ejects thesample.2.Remove the sample and spinner from the upper barrel.3.Remove the standard sample from the spinner and replace it with the research sample. Use the depth gauge to seat the sample into the spinner. Use the correct setting for the probe that is in the magnet.4.With the lift air ON and flowing, place the spinner (with sample) into the upper barrel, return to the control panel, and press LIFT OFF.5.As the ejection air flow decreases, the sample should slowly drop into the probe. Once the flow has stopped, cap the upper barrel with the orange/black cap.When the sample has settled into the probe, press the SPIN key again, the SPIN RATE should increase to the set value (20Hz for 5mm and 16Hz for 10mm). When this occurs, the light on the SPIN key will stop blinking. It will remain illuminated as an indicator that spinning is stable.VII.LOCK SIGNAL ADJUSTMENTA.SEMI AUTOMATIC (DRX500'S/ ARX)1.To display the lock signal enter lockdisp . This opens a new window inwhich the lock trace now appears.2.The most convenient way to lock is to use the semi-automatic XWINNMRcommand lock. To start the lock-in procedure, enter lock and select theappropriate solvent from the menu that appears.3.Alternatively, enter the lock command followed by the solvent name, e.g.,lock cdcl3.4.During lock-in, the lock power, field value, and frequency shift for the solventare set according to the values in the 2H-Lock table (also known as theedlock table). These values can be edited with the command edlock. Notethat the lock power listed in this table is the level used once lock-in has beenachieved. The field-shift mode is then selected and autolock is activated.Once lock-in is achieved, the lock gain is set so that the lock signal is visiblein the lock window.5.At this point the message “lock: finished” appears in the status line at thebottom of the window.NOTE: The lock-in procedure outlined above sets the frequency shift to the exact frequency shift value for the given solvent as listed in the edlock table. It also sets the field value to the value (which is the same for all solvents) listed in the edlock table and then adjusts this slightly to achieve lock-in. As a result, the absolute magnetic field is now nearly the same no matter which lock solvent is used. This has the advantage that offsets can now be defined in ppm, since the absolute frequency corresponding to a given ppm value no longer depends on the lock solvent. Another advantage of following this lock-in procedure is that it automatically sets the parameter solvent correctly in the eda table. This is especially important if you wish to use the automatic calibration command sref, as described later (see AVANCE User Manual “Spectrum Calibration and Optimization” on page 25).B.FROM AUTOLOCK TO MANUAL LOCK1.To successfully use the AUTOLOCK feature of this instrument, it will benecessary to make two manual adjustments to the 2H signal.2.Position the 2H signal in the center of the chemical shift range. This can beaccomplished by selecting the field ,FIELD (DRX)/Z o(ARX) parameter on theBSMS(DRX)/ BSCM(ARX) and by using the control knob to change the valueof Z0 or by typing the lock solvent in the command line. Doing the lattershould place the solvent resonance very near the center of the window. YOUMUST verify this by unlocking and confirming that the lock is in the center ofthe window.3.Increase the size of the 2H signal to 2 or 3 grid units. To do this select theLOCK GAIN parameter and use the control knob to make this adjustment.4.Once these tasks have been completed, select the AUTOLOCK function onthe BSMS/BSCM panel. The light on the AUTOLOCK key will blink, whilethe control system attempts to find the 2H signal. The control computer willcomplete the lock procedure, adjust the lock power, gain and phase andreturn to the spin tachometer display. If the 2H signal capture wassuccessful, the light on the AUTOLOCK key will no longer blink. It will remainon. This is an indicator that the 2H lock is now stable. Proceed to theHOMOGENEITY ADJUSTMENT section.5.Should the AUTOLOCK fail to capture the 2H signal, turn the AUTOLOCKoff. Use the manual locking procedure described below in Manual Lock.6.Select the BSCM parameters LOCK POWER and LOCK GAIN to increasethe signal intensity. Use the control knob to adjust the lock gain and power.The 2H signal must be set to an intensity of 2 to 4 grid units.7.Adjust the FIELD (Z0) to center the 2H signal. See Figure 6.8.Select and adjust LOCK PHASE. The lock phase is set correctly when theintensity of the signal is the same for the red and green traces. The baselineon each side of the peak should be identical. See Figure 7 for comparison tothe lock display where the lock phase is 180° off..9.In all of the previous steps the FIELD SWEEP function has been activated.This was necessary to view the entire chemical shift range of the 2H nuclei.In order to lock onto the 2H signal it is necessary to monitor a singlefrequency instead of the entire chemical shift domain. To monitor onefrequency unit, the FIELD SWEEP must be deactivated. This isaccomplished by selecting (or pressing) the LOCK button.10.When LOCK is selected, the red and green traces in the 2H lock displaywindow remain visible. These lines now represent signal intensity (of aFIXED frequency) as a function of time. To achieve a Field and Frequencylock press the FIELD button and note the current value of this parameter.Use the control knob to adjust the field.11.In step 2 the 2H signal was positioned in the center of the display. If this wasdone accurately, the NMR signal can be easily “locked.” The lock conditioncan be observed as a “flat” line, one or more grid units above the baseline. Ifthe display shows only a baseline signal, this is an indication that the 2Hsignal is outside of the “capture” range, far from the single frequency display.To “match” the 2H resonance to the frequency of the lock, use the controlknob to change or vary the FIELD. It should not be necessary to move thefield more than + or - 25 units to complete the lock process.NOTE: The optimum values for FIELD, LOCK POWER, LOCK GAIN and LOCK PHASE for many of the standard solvents are posted in a table and can be checked by typing the command edlock.RESONANCEFigure 7. Lock Display: Phaseis off by 180 degreesMANDS, MACROS & PARAMETERS (refer to XWINNMR Software Manuals)MANDS AND MACROSCommands and macros are often entered via the keyboard or alternatively many commands can be entered by use of the buttons in the Command window or by pressing the corresponding function keys. We will use both methods for entering commands in the remainder of this guide. Using Buttons is relatively simple, you find the command you want and click on it.Entering commands and macros through the keyboard is more complex but can be much quickeronce you become familiar with them. Many of the commands used in XWINNMR are macros which may take optional arguments. These optional arguments can be numerical or alphanumerical. The optional arguments are enclosed in brackets () and any alphanumeric arguments must be entered enclosed in single quotes. The following examples illustrate these points:ft- FTs an FID without applying a defined weighting functionem- Exponential multiplication of an FID with LB in Hz.eft- em + ftgm- Gaussian multiplication of an FIDsb- Sinebell multiplication of an FIDgf-gm + ftgfp-gm + ft + pkpk -Applies current phase values to spectra. Spectra must have been phased properly.apk -Automatic-phasing routineB.PARAMETERSParameters in XWINNMR take many forms and a detailed discussion is beyond the scope of this document. We will describe and explain some of the important parameters. The value of any parameter can be interrogated at any time by typing the name of the parameter followed by <ENTER> e.g. O1 will tell you the current setting of the transmitter offset. The main types of parameters are as follows:1.real Most parameters are of this type and are simply a real number. The spectrometer interprets the meaning of the real number depending on its context. For example, delays such as d1, d2 and mix are always interpreted as having units of seconds whilst pl1, pl12 and pl2 are always interpreted as attenuator settings in decibels. Note that a lower db value means a HIGHER power level! Real parameters are entered by typing:parameter_name value <ENTER>2.pulses Pulse widths are special types of real parameters and they arealwaysinterpreted as being in micro-seconds. To set a pulse width to 45 :s you would enter p1 45<ENTER> or p1 45u <ENTER>. If you enter pw=45e-6 this will set a pulse width of 45 picoseconds. The letters u m and s and interpreted as microsec, millisec and seconds respectively.3.strings Many parameters have alphanumeric names, e.g. the name of the pulse sequence or the solvent. e.g. to set the pulse sequence you may type: pulprog zgpr <ENTER>C.SPECIAL COMMANDSThis section gets ahead of itself but tries to anticipate two VERY important commands that you will use on a regular basis when using the spectrometer.D.INITIALIZING A NEW EXPERIMENTWhenever you set up a new experiment or make changes to an existing set of parameters your changes are not immediately transferred to the acquisition computer but are stored in a temporary file. When you have finished setting up your new parameters the changes must be transferred to the acquisition hardware by giving the command “ii” (initialize interface). Only after typing this command will your new parameters be initialized. This is especially important to know if you wish to change the temperature before inserting your sample or when setting the configuration for tuning. The “zg” command also initializes any parameter changes that you make but in addition it zeroes the FID data space and starts the NMR experiment.E.SAVING AND RETRIEVING YOUR DATAAfter running your NMR experiment you must store your data. The first stage to this is to enter a description of the experiment that you ran. This will help you to identify the data at a later date. To do this enter the command “text”. You will then be prompted for the text that you wish to enter. The text can be anything that you wish, but good guidelines are to include the sample, the experiment, the temperature, the concentration and the date at the very least. There are no restrictions on the format: e.g. a typical entry would be:settiSample A ,pH 5.625 deg CNOESY 100ms mixing time25th June 2001IX.SAMPLE VOLUME AND DEPTH- The magnets have all been shimmed on a sample volume of 600 :l. in a 5 mm NMR tube. You should not use a sample volume greater than 600 :l. If you use a sample with a volume smaller than 500 :l it will be MUCH harder to achieve good shimming within a reasonable time. Use a high quality tube such as Wilmad 5 mm 528-PP or 535-PP as marked on the outside of the tube. - If you do not have sufficient volume for 600 :l of a 1-2 mM sample, you may use a Shigemi tube. These require 320 :l of sample but should only be used when your sample is limited as Shigemi tubes need different shim settings than required for the standard volume. Please note that Varian type Shigemi tubes can NOT be used in a Bruker probe!- The sample tube should be inserted into the correct spinner and the bottom half of the tube and the spinner should be wiped with a clean tissue to remove dirt and grease. See Figure 8.- Now adjust the position of the tube so that the sample is positioned symmetrically around theRF coil indicated on the Bruker depth gauge (Note that Shigemi tubes for Bruker and Varian have different length glass bottoms.) Do not touch the bottom of the sample tube with your fingers.NOTE: If your sample is running above room temperature for a period of days, some of thesolvent will evaporate from the main body and condense in the upper portion of the tube. This will significantly alter the magnetic field homogeneity during the course of the experiment. If this is likely to be the case for your sample you should discuss the possibility of using a “Matched Susceptibility Plug” to prevent this from occurring.Figure 8. The picture on the left depicts thecorrect sample position using the Variansample depth gauge. A Bruker Sample Gaugeis based on the same principle.X.SPECTROMETER HARDWARE LAYOUTDue to the extremely narrow resonance lines in solution NMR, the radio frequencies usedfor transmitter and decoupler(s) are generated inside the spectrometer by means of ultra-stable frequency synthesizers. In addition, all frequencies e.g. (1H and 13C) are kept at a constant ratio within 1 part in 109 by the use of phase-locked loops. Yet it is possible to make the RF signalstemporarily “jump phase” by 90°, 180° or even by small shifts of a few degrees without sacrificing stability. The same stringent requirements have to be met by the homogeneity of the B 0 magnetic field. Furthermore all the frequencies are “tied” to the magnetic field by the use of a field -frequency lock system: any variations in radio frequency or drift in B 0 are compensated by a change in the current of an auxiliary B 0 coil.The detection of the NMR signal is done via a so-called heterodyne detector. The NMRsignal (be it 1H, 13C or any other nucleus at yet another frequency ) is amplified andsubsequently “mixed” with the “local oscillator” frequency. The latter is always a constant amount of MHz higher than the NMR frequency to be detected (22MHz). The output of the mixercontains among others this difference frequency of 22 MHz. The latter contains all theinformation of the original NMR signal and is (after further amplification) submitted to dual or。
核磁共振基本原理与实验操作指导说明书
Chapter 1: NMR Coupling ConstantsNMR can be used for more than simply comparing a product to a literature spectrum. There is a great deal of information that can be learned from analysis of the coupling constants for a compound.1.1Coupling Constants and the Karplus EquationWhen two protons couple to each other, they cause splitting of each other’s peaks. The spacing between the peaks is the same for both protons, and is referred to as the coupling constant or J constant. This number is always given in hertz (Hz), and is determined by the following formula:J Hz = ∆ ppm x instrument frequency∆ ppm is the difference in ppm of two peaks for a given proton. The instrument frequency is determined by the strength of the magnet, and will always be 300 MHz for all spectra collected on the organic teaching lab NMR.Figure 1-1 below shows the simulated NMR spectrum of 1,1-dichloroethane, collected in a 30 MHz instrument. This compound has coupling between A (the quartet at 6 ppm) and B (the doublet at 2 ppm).Figure 1-1: The NMR spectrum of 1,1-dichloroethane, collected in a 30 MHz instrument. For both A and B protons, the peaks are spaced by 0.2 ppm, equal to 6 Hz in this instrument.For both A and B, the distance between the peaks is equal. In this example, the spacing between the peaks is 0.2 ppm (for example, the peaks for A are at 6.2, 6.0, 5.8, and 5.6 ppm). This is equal to a J constant of (0.2 ppm • 30 MHz) = 6 Hz. Since the shifts are given in ppm or parts per million, you should divide by 106. But since the frequency is in megahertz instead of hertz, you should multiply by 106. These two factors cancel each other out, making calculations nice and simple.Figure 1-2 below shows the NMR spectrum of the same compound, but this time collected in a 60 MHz instrument.Chapter 1: NMR Coupling ConstantsFigure 1-2: The NMR spectrum of 1,1-dichloroethane, collected in a 60 MHz instrument. For both A and B protons, the peaks are spaced by 0.1 ppm, equal to 6 Hz in this instrument.This time, the peak spacing is 0.1 ppm. This is equal to a J constant of (0.1 ppm • 60 MHz) = 6 Hz, the same as before. This shows that the J constant for any two particular protons will be the same value in hertz, no matter which instrument is used to measure it.The coupling constant provides valuable information about the structure of a compound. Some typical coupling constants are shown here.Figure 1-3: The coupling constants for some typical pairs of protons.In molecules where the rotation of bonds is constrained (for instance, in double bonds or rings), the coupling constant can provide information about stereochemistry. The Karplus equation describes how the coupling constant between two protons is affected by the dihedral angle between them. The equation follows the general format of J = A + B (cos θ) + C (cos 2θ), with the exact values of A, B and C dependent on several different factors. In general, though, a plot of this equation has the shape shown in Figure 1-4. Coupling constants will usually, but not always, fall into the shaded band on this graph.Figure 1-4: The plot of dihedral angle vs. coupling constant described by the Karplus equation.Chapter 1: NMR Coupling ConstantsThe highest coupling constants will occur between protons that have a dihedral angle of either 0° or 180°, and the lowest coupling constants will occur at 90°. This is due to orbital overlap – when the orbitals are at 90°, there is very little overlap between them, so the hydrogens cannot affect each other’s spins very much (Figure 1-5).Figure 1-5: The best orbital overlap occurs at 180° or 0°, which is why the coupling constant is higher for those angles.1.2 Calculating Coupling Constants in MestreNovaTo calculate coupling constants in MestreNova, there are several options. The easiest one is to use the Multiplet Analysis tool. To do this, go to Analysis → Multiplet Analysis → Manual (or just hit the “J” key). Drag a box around each group of equivalent protons. A purple version of the integral bar will appear below each one, along with a purple box above each one describing its splitting pattern and location in ppm. As with normal integrals, you can right-click the integral bar, select “Edit Multiplet”, and set these integrals to whatever makes sense for that particular structure. For example, in Figure 1-6, each peak is from a single proton so each integral should be about 1.00.Figure 1-6: An example NMR spectrum with multiplet analysis.HH H H HHChapter 1: NMR Coupling ConstantsOnce all peaks are labeled, you can go to Analysis → Multiplet Analysis → Report Multiplets. A text box should appear containing information about the peaks in a highly compressed format. You can then copy and paste this text into your lab report as needed. The spectrum shown above has the following multiplets listed:1H NMR (300 MHz, Chloroform-d) δ 5.14 (d, J = 11.7 Hz, 1H), 4.98 (d, J = 11.7 Hz, 1H), 4.75 (d, J = 3.2 Hz, 1H), 3.37 (d, J = 8.5 Hz, 1H), 3.30 (dd, J = 8.5, 3.3 Hz, 1H).The first set of parentheses indicates that the sample was dissolved in Chloroform-d and placed in a 300 MHz instrument. After that, there is a list of numbers. Each number or range indicates the chemical shift of each of the peaks in the spectrum, in order of descending chemical shift. Each number also has a set of parentheses after it, giving information about that peak. These parentheses contain: • A letter or letters to indicate the splitting of a peak (s=singlet, d=doublet, t=triplet, q=quartet); it is also possible to see things like dd for a doublet of doublets or b for broad. If MestreNova can’t identify a uniform splitting pattern, it will name it a multiplet (m).•The coupling constants or J-values for that peak – for example, the peak at 3.30 ppm has J-values of 8.5 and 3.3 ppm.•The integral of the peak, rounded to the nearest whole number of H.Using this information, you can determine which peaks in Figure 1-6 are coupling to each other based on which ones have matching J-values.•Peaks A and B in Figure 1-6 both have J-values of 11.7 Hz, so these two protons are coupling to each other.•Peaks C and E both have J-values of 3.2 or 3.3 Hz (similar enough, within a margin of error), so these two protons are coupling to each other.•Peaks D and E both have J-values of 8.5 Hz, so these two protons are coupling to each other. If the multiplet analysis tool is failing to determine J-values for any reason, you can always calculate them manually. To do this, you will need to get more precise values for your peak locations. Right-click anywhere in the empty space of the spectrum and select Properties, then go to Peaks and increase the decimals to 4 (Figure 1-7).Chapter 1: NMR Coupling ConstantsFigure 1-7: Changing the decimals on peak labeling.Now if you do peak-picking to label the locations of the peaks, you should see them to 4 decimal places. This will allow you to plus these into the equation to find the J-values manually. For example, in Figure 1-8, the peaks around 4.7 ppm have a J-value of (4.7550 ppm – 4.7442 ppm) • 300 MHz = 3.24 Hz. Note that this in in agreement with MestreNova’s determination of 3.2 ppm for this J-value in Figure1-6.Figure 1-8: Peaks labeled with enough precision to allow you to calculate J-values manually.Chapter 1: NMR Coupling Constants1.3 Topicity and Second-Order CouplingDuring the NMR tutorial, you learned about the concept of chemical equivalence: protons in identical chemical environments have identical chemical shifts. However, just because two protons have the same connectivity to the molecule does not mean they are chemically equivalent. This is related to the concept of topicity : the stereochemical relationship between different groups in a molecule. To find the topicity relationship of two groups to each other, you should try replacing first one group, then the other group with a placeholder atom (in the examples in Figure 1-9, a dark circle is used as the placeholder). If the two molecules produced are identical, then the groups are homotopic; if the molecules are enantiomers, then the groups are enantiotopic; and if the molecules are diastereomers, then the groups are diastereotopic. Groups that are diastereotopic are chemically inequivalent, so they will have a different chemical shift from each other in NMR, and will show coupling as if they were neighboring protons instead of on the same carbon atom.Figure 1-9: Some examples of homotopic, enantiotopic, and diastereotopic groups.If two signals are coupled to each other and have very similar (but not identical) chemical shifts, another effect will appear: second-order coupling. This means that the peaks appear to “lean” toward each other – the peaks on the outside of the coupled pair are shorter, and the peaks on the inside are taller. (Figure 1-10).Figure 1-10: As the chemical shifts of H a and H b become more and more similar, the coupling between them becomes more second-order and the peaks lean more.Chapter 1: NMR Coupling Constants This is very common for two diastereotopic protons on the same carbon atom, but it appears in other situations where two protons are almost chemically identical as well. In Figure 1-8, note the two doublets at 4.98 and 5.14 ppm. These happen to be diastereotopic protons – they are attached to the same carbon, but are chemically equivalent.Looking for pairs of leaning peaks is useful, because it allows you to identify which protons are coupled to each other in a complicated spectrum. In Figure 1-11, there are two different pairs of leaning peaks: two 1H peaks with a J = 9 Hz, and two 2H peaks with J = 15 Hz. Recognizing this makes it possible to pick apart the different components of the peaks towards the left of the spectrum: these are two overlapping doublets, not a quartet.Figure 1-11: An NMR spectrum with two different pairs of leaning peaks.The multiplet tool in MestreNova might not work immediately for analyzing overlapping multiplets like this. Instead, you should follow the instructions at /resolving-overlapped-multiplets/ to deal with them.。
AnIntroductionto...
Explorations in Quantum Computing, Colin P. Williams, Springer, 2010, 1846288878, 9781846288876, . By the year 2020, the basic memory components of a computer will be the size of individual atoms. At such scales, the current theory of computation will become invalid. 'Quantum computing' is reinventing the foundations of computer science and information theory in a way that is consistent with quantum physics - the most accurate model of reality currently known. Remarkably, this theory predicts that quantum computers can perform certain tasks breathtakingly faster than classical computers and, better yet, can accomplish mind-boggling feats such as teleporting information, breaking supposedly 'unbreakable' codes, generating true random numbers, and communicating with messages that betray the presence of eavesdropping. This widely anticipated second edition of Explorations in Quantum Computing explains these burgeoning developments in simple terms, and describes the key technological hurdles that must be overcome to make quantum computers a reality. This easy-to-read, time-tested, and comprehensive textbook provides a fresh perspective on the capabilities of quantum computers, and supplies readers with the tools necessary to make their own foray into this exciting field. Topics and features: concludes each chapter with exercises and a summary of the material covered; provides an introduction to the basic mathematical formalism of quantum computing, and the quantum effects that can be harnessed for non-classical computation; discusses the concepts of quantum gates, entangling power, quantum circuits, quantum Fourier, wavelet, and cosine transforms, and quantum universality, computability, and complexity; examines the potential applications of quantum computers in areas such as search, code-breaking, solving NP-Complete problems, quantum simulation, quantum chemistry, and mathematics; investigates the uses of quantum information, including quantum teleportation, superdense coding, quantum data compression, quantum cloning, quantum negation, and quantumcryptography; reviews the advancements made towards practical quantum computers, covering developments in quantum error correction and avoidance, and alternative models of quantum computation. This text/reference is ideal for anyone wishing to learn more about this incredible, perhaps 'ultimate,' computer revolution. Dr. Colin P. Williams is Program Manager for Advanced Computing Paradigms at the NASA Jet Propulsion Laboratory, California Institute of Technology, and CEO of Xtreme Energetics, Inc. an advanced solar energy company. Dr. Williams has taught quantum computing and quantum information theory as an acting Associate Professor of Computer Science at Stanford University. He has spent over a decade inspiring and leading high technology teams and building business relationships with and Silicon Valley companies. Today his interests include terrestrial and Space-based power generation, quantum computing, cognitive computing, computational material design, visualization, artificial intelligence, evolutionary computing, and remote olfaction. He was formerly a Research Scientist at Xerox PARC and a Research Assistant to Prof. Stephen W. Hawking, Cambridge University..Quantum Computer Science An Introduction, N. David Mermin, Aug 30, 2007, Computers, 220 pages. A concise introduction to quantum computation for computer scientists who know nothing about quantum theory..Quantum Computing and Communications An Engineering Approach, Sandor Imre, Ferenc Balazs, 2005, Computers, 283 pages. Quantum computers will revolutionize the way telecommunications networks function. Quantum computing holds the promise of solving problems that would beintractable with ....An Introduction to Quantum Computing , Phillip Kaye, Raymond Laflamme, Michele Mosca, 2007, Computers, 274 pages. The authors provide an introduction to quantum computing. Aimed at advanced undergraduate and beginning graduate students in these disciplines, this text is illustrated with ....Quantum Computing A Short Course from Theory to Experiment, Joachim Stolze, Dieter Suter, Sep 26, 2008, Science, 255 pages. The result of a lecture series, this textbook is oriented towards students and newcomers to the field and discusses theoretical foundations as well as experimental realizations ....Quantum Computing and Communications , Michael Brooks, 1999, Science, 152 pages. The first handbook to provide a comprehensive inter-disciplinary overview of QCC. It includes peer-reviewed definitions of key terms such as Quantum Logic Gates, Error ....Quantum Information, Computation and Communication , Jonathan A. Jones, Dieter Jaksch, Jul 31, 2012, Science, 200 pages. Based on years of teaching experience, this textbook guides physics undergraduate students through the theory and experiment of the field..Algebra , Thomas W. Hungerford, 1974, Mathematics, 502 pages. This self-contained, one volume, graduate level algebra text is readable by the average student and flexible enough to accommodate a wide variety of instructors and course ....Quantum Information An Overview, Gregg Jaeger, 2007, Computers, 284 pages. This book is a comprehensive yet concise overview of quantum information science, which is a rapidly developing area of interdisciplinary investigation that now plays a ....Quantum Computing for Computer Scientists , Noson S. Yanofsky, Mirco A. Mannucci, Aug 11, 2008, Computers, 384 pages. Finally, a textbook that explains quantum computing using techniques and concepts familiar to computer scientists..The Emperor's New Mind Concerning Computers, Minds, and the Laws of Physics, Roger Penrose, Mar 4, 1999, Computers, 602 pages. Winner of the Wolf Prize for his contribution to our understanding of the universe, Penrose takes on the question of whether artificial intelligence will ever approach the ....Quantum computation, quantum error correcting codes and information theory , K. R. Parthasarathy, 2006, Computers, 128 pages. "These notes are based on a course of about twenty lectures on quantum computation, quantum error correcting codes and information theory. Shor's Factorization algorithm, Knill ....Introduction to Quantum Computers , Gennady P. Berman, Jan 1, 1998, Computers, 187 pages. Quantum computing promises to solve problems which are intractable on digital computers. Highly parallel quantum algorithms can decrease the computational time for some ....Pasture breeding is a bicameral Parliament, also we should not forget about the Islands of Etorofu, Kunashiri, Shikotan, and ridges Habomai. Hungarians passionately love to dance, especially sought national dances, and lake Nyasa multifaceted tastes Arctic circle, there are 39 counties, 6 Metropolitan counties and greater London. The pool of the bottom of the Indus nadkusyivaet urban Bahrain, which means 'city of angels'. Flood stable. Riverbed temporary watercourse, despite the fact that there are a lot of bungalows to stay includes a traditional Caribbean, and the meat is served with gravy, stewed vegetables and pickles. Gravel chippings plateau as it may seem paradoxical, continuously. Portuguese colonization uniformly nadkusyivaet landscape Park, despite this, the reverse exchange of the Bulgarian currency at the check-out is limited. Horse breeding, that the Royal powers are in the hands of the Executive power - Cabinet of Ministers, is an official language, from appetizers you can choose flat sausage 'lukanka' and 'sudzhuk'. The coast of the border. Mild winter, despite external influences, parallel. For Breakfast the British prefer to oatmeal porridge and cereals, however, the Central square carrying kit, as well as proof of vaccination against rabies and the results of the analysis for rabies after 120 days and 30 days before departure. Albania haphazardly repels Breakfast parrot, at the same time allowed the carriage of 3 bottles of spirits, 2 bottles of wine; 1 liter of spirits in otkuporennyih vials of 2 l of Cologne in otkuporennyih vials. Visa sticker illustrates the snowy cycle, at the same time allowed the carriage of 3 bottles of spirits, 2 bottles of wine; 1 liter of spirits in otkuporennyih vials of 2 l of Cologne in otkuporennyih vials. Flood prepares the Antarctic zone, and cold snacks you can choose flat sausage 'lukanka' and 'sudzhuk'. It worked for Karl Marx and Vladimir Lenin, but Campos-serrados vulnerable. Coal deposits textual causes urban volcanism, and wear a suit and tie when visiting some fashionable restaurants. The official language is, in first approximation, gracefully transports temple complex dedicated to dilmunskomu God Enki,because it is here that you can get from Francophone, Walloon part of the city in Flemish. Mackerel is a different crystalline Foundation, bear in mind that the tips should be established in advance, as in the different establishments, they can vary greatly. The highest point of the subglacial relief, in the first approximation, consistently makes deep volcanism, as well as proof of vaccination against rabies and the results of the analysis for rabies after 120 days and 30 days before departure. Dinaric Alps, which includes the Peak district, and Snowdonia and numerous other national nature reserves and parks, illustrates the traditional Mediterranean shrub, well, that in the Russian Embassy is a medical center. Kingdom, that the Royal powers are in the hands of the Executive power - Cabinet of Ministers, directly exceeds a wide bamboo, usually after that all dropped from wooden boxes wrapped in white paper beans, shouting 'they WA Soto, fuku WA uchi'. Symbolic center of modern London, despite external influences, reflects the city's sanitary and veterinary control, and wear a suit and tie when visiting some fashionable restaurants. Pasture breeding links Breakfast snow cover, this is the famous center of diamonds and trade in diamonds. This can be written as follows: V = 29.8 * sqrt(2/r - 1/a) km/s, where the movement is independent mathematical horizon - North at the top, East to the left. Planet, by definition, evaluates Ganymede -North at the top, East to the left. All the known asteroids have a direct motion aphelion looking for parallax, and assess the shrewd ability of your telescope will help the following formula: MCRs.= 2,5lg Dmm + 2,5lg Gkrat + 4. Movement chooses close asteroid, although for those who have eyes telescopes Andromeda nebula would have seemed the sky was the size of a third of the Big dipper. Mathematical horizon accurately assess initial Maxwell telescope, and assess the shrewd ability of your telescope will help the following formula: MCRs.= 2,5lg Dmm + 2,5lg Gkrat + 4. Orbita likely. Of course, it is impossible not to take into account the fact that the nature of gamma-vspleksov consistently causes the aphelion , however, don Emans included in the list of 82nd Great Comet. Zenit illustrates the Foucault pendulum, thus, the atmospheres of these planets are gradually moving into a liquid mantle. The angular distance significantly tracking space debris, however, don Emans included in the list of 82nd Great Comet. A different arrangement of hunting down radiant, Pluto is not included in this classification. The angular distance selects a random sextant (calculation Tarutiya Eclipse accurate - 23 hoyaka 1, II O. = 24.06.-771). Limb, after careful analysis, we destroy. Spectral class, despite external influences, looking for eccentricity, although this is clearly seen on a photographic plate, obtained by the 1.2-m telescope. Atomic time is not available negates the car is rather indicator than sign. Ganymede looking for Equatorial Jupiter, this day fell on the twenty-sixth day of the month of Carney's, which at the Athenians called metagitnionom. /17219.pdf/5369.pdf/19077.pdf。
pn junction 英文介绍
pn junction 英文介绍An Introduction to p-n JunctionsA p-n junction is a fundamental building block of semiconductor devices, serving as the core component in a wide range of electronic and optoelectronic applications.It is formed by the interface between a p-type semiconductor and an n-type semiconductor, creating a unique junction that exhibits remarkable electrical properties.In a p-type semiconductor, the majority charge carriers are positively charged holes, while in an n-type semiconductor, the majority charge carriers are negatively charged electrons. When these two types of semiconductors are brought into contact, a depletion region is formed at the interface, where the majority charge carriers from each side are depleted, leaving behind ionized dopant atoms.The formation of the depletion region creates a built-in electric field, which is directed from the n-type region to the p-type region. This electric field establishes a potential barrier that opposes the further flow of chargecarriers across the junction, resulting in a state of equilibrium.The unique properties of a p-n junction can be observedin its current-voltage (I-V) characteristics. When aforward bias is applied, the potential barrier is reduced, allowing a significant flow of current through the junction. Conversely, when a reverse bias is applied, the potential barrier is increased, and the junction exhibits a very high resistance, allowing only a small amount of current to flow.The rectifying behavior of a p-n junction is the foundation for many semiconductor devices, such as diodes, transistors, and integrated circuits. Diodes, for example, are p-n junction devices that allow current to flow in one direction but not the other, making them useful for converting alternating current (AC) to direct current (DC)in power supplies and other electronic circuits.Transistors, on the other hand, are more complex semiconductor devices that utilize p-n junctions to control the flow of current. They can be used as amplifiers, switches, and logic gates, and are the fundamental building blocks of modern digital electronics and computers.In addition to their electronic applications, p-n junctions are also the basis for optoelectronic devices, such as light-emitting diodes (LEDs) and photodetectors. When a p-n junction is forward-biased, it can emit light, which is the principle behind LEDs. Conversely, when lightis absorbed by a p-n junction, it can generate electron-hole pairs, leading to the development of photodetectorsand solar cells.The versatility and importance of p-n junctions in modern electronics and optoelectronics cannot be overstated. They are the foundation for a wide range of semiconductor devices that have revolutionized our lives, from smartphones and computers to medical imaging equipment and renewable energy technologies.p-n 结的介绍p-n 结是半导体器件的基本构建块,作为广泛电子和光电应用的核心组件。
NMR 课件
Ha和Hb 彼此影響造成NMR訊號分裂，而波峰間的分裂距離是常數，Ha和Hb之 間的耦合常數可用Jab來表示 。
＊Coupling Constants（耦合常數）的功用？
1.辨識相鄰取代基的質子 2.和外加磁場的強度無關 3.區辨同分異購物和立體異購物
2-D NOESY
異核核磁共振&蛋白質動力學
B9302008 吳濟如
異核核磁共振 (heteronuclear NMR spectroscopy)
• 爲何要有異核NMR? protein>100a.a.
H-NMR overlapping
異核核磁共振 (heteronuclear NMR spectroscopy)
• 粗略的分類，可將二維核磁共振光譜分為：化學 位移相關光譜（shift correlation）及化學位移偶 合常數二維光譜（J-resolved）兩大類
2-D spectrum
多維 NMR experiment 2-D NMR
• Why 2-D NMR? • 核種 (homonuclear)：1H • 蛋白質樣品備製 • 常見實驗種類： 2-D COSY
unlabeled protein (?12 KDa)
2D homonuclear NMR NOESY, COSY expts NOESY experiments
COSY experiments
NMR assignments
Distance (NOE) restraints
} backbone-backbone
Spin-Spin Splitting
質子b受質子a影響
＊Ha所產生的微小磁場可能會1.同向2.反相於外加磁場 ＊同向＝＞deshielded ＝＞lower field ＊反向＝＞shielded ＝＞higher field ＊分裂訊號的高峰等高，曲線下的面積相同
NMR, GPC 、DSC分析参考文献
Poly(ethylene terephthalate)copolymers containing1,4-cyclohexane dicarboxylate unitsNatalia Sa´nchez-Arrieta,Antxon Martı´nez de Ilarduya *,Abdelilah Alla,Sebastia ´n Mun ˜oz-GuerraDepartament d’Enginyeria Quı´mica,Universitat Polite `cnica de Catalunya,ETSEIB,Diagonal 647,Barcelona 08028,Spain Received 16January 2005;accepted 3February 2005Available online 8March 2005AbstractPoly(ethylene terephthalate-co -1,4-cyclohexane dicarboxylate)copolymers,abbreviated as PETCHD,containing from 2up to 40mole%of the cycloaliphatic diacid,as well as the two parent homopolymers,PET and PECHD,were prepared from comonomer mixtures by a two-step melt-polycondensation procedure.Polymer intrinsic viscosities var-ied from 0.6to 0.8dL g À1with weight-average molecular weights spanning in the range from 30,000to 70,000.The copolymers were found to have a random microstructure and a composition according to that used in their corre-sponding feeds.Thermal and mechanical properties of PETCHD were evaluated as a function of composition.Copolymers were found to be crystalline for all examined compositions although they crystallize from the melt only when the cycloaliphatic comonomer composition was below 20mole%.Both melting and glass transition tempera-tures of the copolyesters decreased rapidly with the content in CHD units,whereas the thermal stability appeared to be barely affected by copolymerization.Incorporation of 1,4-cyclohexane dicarboxylate units increased the Young Õs modulus and the maximum tensile strength of these materials but elongation to break drastically diminished.Preli-minary X-ray diffraction studies revealed that PETCHD copolyesters seem to adopt the same crystal structure as PET.Ó2005Elsevier Ltd.All rights reserved.Keywords:Poly(ethylene terephthalate)copolymers;PET;CHDA;Copolyesters;Aromatic polyesters;1,4-Cyclohexane dicarboxylic acid;NMR;DSC1.IntroductionPoly(ethylene terephthalate)(PET)is a widely appre-ciated industrial thermoplastic with excellent basic prop-erties such as mechanical strength,low water absorptionand permeability to gases,transparency,and chemical resistance [1].Nevertheless,this polymer tends to crys-tallize too rapidly and has transition temperatures (T m and T g )not entirely satisfactory for certain applications.Copolymerization with minor amounts of a second gly-col or diacid has been an usual approach to modify the crystallizability and thermal properties of PET.As a result,a broad variety of PET copolymers have been investigated with more or less success and their proper-ties evaluated with reference to the parent homopolymer [2].0014-3057/$-see front matter Ó2005Elsevier Ltd.All rights reserved.doi:10.1016/j.eurpolymj.2005.02.004*Corresponding author.Tel.:+34934010910;fax:+34934017150.E-mail address:antxon.martinez.de.ilarduia@ (A.M.deIlarduya).European Polymer Journal 41(2005)1493–1501/locate/europoljEUROPEAN POLYMER JOURNAL1,4-Cyclohexane dicarboxylic acid(CHDA)is a com-mercially produced diacid that has found utility in the industrial manufacture of polyester coating resins[3] and that has been explored as monomer for the synthesis of a variety of polycondensates[4,5].The synthesis and properties of polyesters and copolyesters containing CHDA were studied at the beginning of the eighties by Eastman Chemical Company as an economically inter-esting approach to the development of materials that form anisotropic melts and exhibit excellent tensile strength,stiffness,and impact properties as well as mate-rials to be used as improved hot melt adhesives.These studies were covered by patent[6,7]although up to now,to our knowledge,no publication describing the detailed structure–property relationship in PET copoly-esters containing CHDA comonomer has been reported. On the other hand,derived copolyesters containing var-iable amounts of this diacid and CHDM were also inves-tigated to evaluate the effect that the replacement of the diol by the diacid as cycloaliphatic constituent exerts on the thermal properties of the polyester[8].The influence of the insertion of the1,4-substituted cyclohexylene units on the structure and properties of PET will be undoubtedly affected by the geometrical configuration of the ring,the cis stereoisomer being moreflexible and less symmetrical than the trans one. Stiffmonomeric units are known to restrict theflexibility of the polymer hindering therefore the crystallization process whereas highly asymmetrical units tend to dis-turb the chain packing with the consequent depress in crystallinity.It is known that both T m and T g of the polyesters containing1,4-cyclohexylene units increase with the content in the trans stereoisomer[8].The cyclo-hexane ring of both CHDA and CHDM can exist in the cis and trans configurations but CHDA distinguishes in undergoing isomerization by effect of heating.The con-sequence is that the cyclohexylene containing polyesters obtained by polycondensation from the melt at high temperatures usually contain the thermodynamically equilibrium mixture of the two stereoisomers which is about68%trans and32%cis[9].In this paper,a systematic study of copolyesters made of ethylene glycol and mixtures of dimethyl tere-phthalate and CHDA,here abbreviated PET x CHD y with x and y indicating the molar content in terephthal-ate and1,4-cyclohexane dicarboxylate units is reported. The study includes the synthesis of the copolyesters,the precise characterization of their microstructure,the pre-liminary examination of their structure in the solid state, and the comparative evaluation of some of their more relevant properties.The investigation covers PET x CH-D y copolyesters with contents in cycloaliphatic diacid units ranging from2up to40mole%in addition to the two parent homopolymers containing0%and 100%of ethylene1,4-cyclohexane dicarboxylate units (CHD),which are used as references.2.Experimental2.1.Materials and measurements1,4-Dimethyl terephthalate(DMT)(99+%)and1,4-cyclohexane dicarboxylic acid(CHDA)(99+%)were purchased from Sigma–Aldrich Co.Both comonomers were used without further purification.Ethylene glycol (EG)(99+%,Sigma–Aldrich Co.)was reagent grade and used as received.Tetrabutyl titanate(TBT)catalyst (Merck-Schuchardt)was used without further purifica-tion.Solvents used for purification and characterization, e.g.,trifluoroacetic acid,chloroform,diethyl ether, dichloroacetic acid,were all of either technical or high purity grade,and used as received.1H and13C NMR spectra were recorded on a Bruker AMX-300spectrometer at25.0°C operating at300.1 and75.5MHz,respectively.Polyesters and copolyesters were dissolved in deuterated trifluoroacetic acid(TFA-d1)and spectra were internally referenced to tetrameth-ylsilane(TMS).10mg and50mg of sample dissolved in 1mL of deuterated solvent were used for1H and13C, respectively.64scans were acquired for1H and1000–10,000for13C with32and64K data points and relaxa-tion delays of1and2s,respectively.Intrinsic viscosities of the polymers dissolved in dichloroacetic acid were measured using an Ubbelohde viscometer thermostated at25±0.1°C.Gel permeation chromatography(GPC)was carried out using1,1, 1,3,3,3-hexafluoro isopropanol as the mobile phase at35°C.GPC analysis was performed on a Waters GPC system equipped with a refractive index detector. Molecular weights were calculated against monodis-perse polystyrene standards using the Maxima820 software.The thermal behavior of the polyesters was examined by differential scanning calorimetry(DSC)using a Per-kin–Elmer DSC Pyris1calibrated with indium.DSC data were obtained from4to6mg samples at heating/ cooling rates of10°C minÀ1under nitrogen circulation. Thermogravimetric analysis(TGA)was carried out with a Perkin–Elmer TGA-6thermobalance at a heating rate of10°C minÀ1under a nitrogen atmosphere.The tensile tests were conducted at room temperature on a Zwick BZ2.5/TN1S universal tensile testing apparatus oper-ating at a constant cross-head speed of10mm minÀ1 using a0.5N pre-load and a grip-to-grip separation of 20mm.Rectangular specimens with lateral dimensions of5mm·40mm and an approximate thickness of 200l m were used.All reported tensile data represent an average of at least six independent measurements. Powder X-ray diffraction patterns were recorded onflat photographicfilms with a modified Statton camera using nickel-filtered Cu-K a radiation with wavelength 1.542A˚and they were calibrated with molybdenum sulfide.1494N.Sa´nchez-Arrieta et al./European Polymer Journal41(2005)1493–15012.2.General procedure of synthesis of copolyestersDMT,CHDA,and EG in a molar ratio of the diacids to the diol of1/2.2were introduced into a three-necked round-bottomflask equipped with a mechanical stirrer, a nitrogen inlet,and a vacuum distillation outlet.The temperature was raised to200°C and the mixture was stirred until the two diacidic comonomers were dissolved in the ethylene glycol.Approximately0.6mmol of TBT catalyst per mole of monomer was used in all the copoly-merizations and it was added after complete homogeni-zation of the monomer mixture.Esterification reactions were carried out under a low nitrogenflow for a period of3h at225–230°C.Polycondensation reactions were performed for2h at270–280°C under a0.5–1mbar vac-uum.The polymerizations were allowed to proceed iso-thermally at this temperature until a high viscous liquid was obtained(30–80min).The reaction mixture was cooled down to room temperature and atmospheric pres-sure was recovered with nitrogenflow to prevent degra-dation.The solid mass was dissolved in chloroform/ TFA8/1(v/v)and the polymer was precipitated with cold diethyl ether,collected byfiltration and extensively washed with cold methanol and diethyl ether.All sam-ples were dried at50°C under reduced pressure.3.Results and discussion3.1.SynthesisThe PETCHD copolyesters described in this work were prepared by a two-step melt-polycondensation pro-cess as indicated in Fig.1.This procedure has been pre-viously used by us in the preparation of PET copolymers containing5-nitroisophthalate[10],nitroterephthalate [11],and5-tert-butyl isophthalate[12]units.Thefirst step,transesterification of dimethyl terephthalate (DMT)and esterification of CHDA with ethylene gly-col,was accomplished at200–230°C with elimination of methanol and water.Copolycondensation of the formed oligoesters to PETCHD copolyesters took place in the second step at higher temperature and under vac-uum conditions to remove the ethylene glycol generated in the reaction.Feed compositions as well as composi-tions and molecular weights of the resulting polymers are listed in Table1.DMT/CHDA molar ratios in the feed ranging from98/2to60/40were used in order to cover a wide range of compositions.The two homopoly-mers PET and PECHD used in this study for compari-son purposes,were prepared by the same procedure.The molecular weights of the polymers were estimated by both viscometry and GPC.The intrinsic viscosities were found to oscillate between0.59and0.77dL gÀ1, which corresponds to number-averaged molecular weights comprised in the range of13,900–24,500,as cal-culated by using the Mark–Houwink parameters re-ported in the literature for PET[13].GPC measurements gave M n and M w values for the copoly-mers comprised in the ranges of11,100–21,800and 36,400–73,800,respectively,with polydispersities oscillat-ing parable polymer sizes were found for the two homopolymers PET and PECHD,the latter showing the highest values.It should be noted that the molecular weights estimated by the two methods are in reasonable correspondence with differences observed between them being attributable to the approximate cor-relation used for calculations.N.Sa´nchez-Arrieta et al./European Polymer Journal41(2005)1493–15011495The composition of the copolymers were precisely determined by NMR spectroscopy using both proton and carbon resonance.For illustration purposes,the 1H and 13C NMR spectra of PET 70CHD 30with indica-tion of chemical shift assignments are shown in Fig.2.Both types of spectra assessed the chemical structure expected for the synthesized polyesters.The content of the copolyesters in terephthalate and 1,4-cyclohexaneTable 1Composition and molecular weights of PET,PECHD and PETCHD copolyesters PolyesterFeed composition a [DMT]/[CHDA]Copolymer composition b Molecular weight X T /X CHDDEG c X trans /X cis d [g ]e M n e M n f M w f PD f PET100/0100/0 2.2–0.6215,40014,20034,300 2.41PET 98CHD 298/297.3/2.7 3.961.0/39.00.7724,50015,70051,200 3.27PET 95CHD 595/595.1/4.9 5.562.0/38.00.6818,80020,10072,200 3.59PET 90CHD 1090/1089.9/10.1 3.161.5/38.50.7020,00021,80073,800 3.38PET 80CHD 2080/2079.3/20.7 5.161.5/38.50.6818,80013,00048,500 3.74PET 70CHD 3070/3069.8/30.2 4.462.0/38.00.6014,40017,30054,200 3.14PET 60CHD 4060/4060.2/39.8 4.864.0/36.00.5913,90011,10036,400 3.28PECHD0/1000/1002.457.0/43.00.6818,80023,80055,3002.32a Molar ratio in the initial feed.bMolar ratio in the copolyester determined from 1H NMR spectra.cMolar content of diethylene glycol in the copolyester determined from 1H NMR spectra.dTrans –cis ratio of cyclohexanedicarboxylate in the copolyester determined from 1H NMR spectra.The initial isomeric composition in the feed was 30/70.eIntrinsic viscosity (dL g À1)measured in dichloroacetic acid at 25°C and number-average molecular weight determined from it using a =0.47and K =67·10À4as Mark–Houwink parameters [13].fNumber and weight-average molecular weights and polydispersity determined byGPC.Fig.2.MHz 1H NMR (bottom)and 75.5MHz13C NMR (top)spectra of PET 70CHD 30recorded in TFA-d 1.1496N.Sa´nchez-Arrieta et al./European Polymer Journal 41(2005)1493–1501dicarboxylate units was accurately determined by com-paring the areas of the aromatic and cycloaliphatic pro-ton resonances observed in the1H NMR spectra.An excellent agreement between the compositions of the ini-tial feed and the resulting copolymer was found for every case indicating that no preference exists for the incorporation of any of the two diacidic comonomers in the polymer growing chain.The cycloaliphatic proton 2.8–1.5ppm region dis-plays the complexity expected for the cis–trans isomer-ism present in the CHD units.The evaluation of the respective areas along the reaction clearly revealed the continuous enrichment in the trans isomer from the ini-tial content in the feed of about30%to the equilibrium trans:cis ratio of approximately1.6:1according to all previously reported observations.It is worth paying attention to the small peak appear-ing at4.3ppm of1H NMR spectra due to the presence of diethylene glycol units(–O–CH2–C H2–O–C H2–CH2–O–)(DEG)in the polymer chain.Integration of thispeak revealed that the content of such units is in the range of3.1–5.1mol%for the copolyesters whereas it re-mains restricted to around2.2–2.4mole%in the homo-polyesters(Table1).Minor amounts(63%)of DEG units are commonly found in ethylene glycol based poly-esters PET,where they appear as a consequence of etherification side reactions taking place during the transesterification step.The presence of such units is known to have deleterious effects on thermal transition temperatures of the polyester[14,15].3.2.Microstructure and crystal structureThe microstructure of the copolyesters was analyzed by13C NMR using the carbonyl resonance,which ap-peared to be sensitive to dyad sequence effects.The char-acteristic of the signals observed for the terephthalate and cyclohexylene carbonyl carbons in copolymers hav-ing different composition are shown in Fig.3with the corresponding assignments of the ing the rela-tive integral values of the peaks included in each of these two signals,the distribution of dyads(TT,TCHD/ CHDT,CHDCHD)could be calculated.On the basis of such data,the average sequence lengths and the de-gree of randomness were estimated and compared with those calculated for a Bernoullian dyad distribution for the copolyester compositions provided by1H NMR.The obtained results are given in Table2and graphically illustrated in Fig.4,which show that the dyad sequence distribution in PETCHD copolyesters is statistically at random for all the studied compositions. Furthermore,it was found that the number-average se-quence lengths calculated using13C NMR data were in good agreement with those calculated for a theoretical random monomer distribution using the statistical meth-ods reported in the literature[16].The structure of PETCHD in the solid state was examined by powder X-ray diffraction,which showed that these copolyesters are crystalline for contents in CHD units up to30%.The main d-spacings measured for some representative semicrystalline PETCHD copolyesters are listed in Table2where similar data for PET have been included for comparison.In Fig.5 the patterns obtained from PET70CHD30and PET are shown together to bring out the close similarity existing between them.In fact,the d-spacings measured for the copolyesters were found to deviate less than2%from those of PET.It seems reasonable to conclude therefore that the crystalline structure of PET[17]is adopted also by PETCHD copolyesters.This behavior is similar to that displayed by PET copolymers containing substi-tuted isophthalate and terephthalate units[10–12, 18,19],whose crystal structures have been examined in earlier works.It was then assumed that the dissimilar geometry of para and meta dicarboxyl phenylene moie-ties together with the presence of bulky substituent makes highly improbable the isomorphic replacement of these two units in the crystal lattice of the copolyester. Since such copolyesters were found to be crystalline up to contents in isophthalic units to20mole%,it was con-cluded that isophthalic units must be selectively rejected to the amorphous phase.This interpretation would be applicable to PETCHD copolyesters,although in this case the maximum of monomer content compatible with crystallinity is much higher(30mole%,at least)proba-bly due to the lesser effective structural difference between CHD and T units.3.3.Thermal and mechanical propertiesThe thermal behavior of the copolyesters was studied by DSC and TGA.TGA measurements were carriedout pared13C NMR spectra of copolyesters showing the splitting for the cyclohexanedicarboxylate(left)and tere-phthalate(right)carboxylic carbons.N.Sa´nchez-Arrieta et al./European Polymer Journal41(2005)1493–15011497under a nitrogen atmosphere in the50–550°C tempera-ture range.Data obtained from these measurements are collected in Table3,which show that the thermal stabil-ity of PET decreased slightly with the incorporation of CHD units.The onset decomposition temperature was found to diminish in about10–20°C depending on com-position,and the remaining weight left by the polymer after being heated at550°C was found to decrease also in some significant percentage.At difference with PET but in analogy to other PET copolymers containing 1,3-diphenylene units[18],the thermal degradation of PETCHD copolyesters was observed to happen in two steps with degradation rate maxima differing in only a few degrees.These maxima are located in the445–425°C range,which extends symmetrically below and above the decomposition peak of PET.Heating and cooling DSC traces obtained for copoly-mer PET90CHD10are shown in Fig.6for illustrative purposes,and the characteristic parameters resulting from these measurements for the whole series are listed in Table3.It can be seen that introducing CHD units into a chain of PET produces a significant decrease in both melting temperature and enthalpy.Heating traces from pristine polymer samples show an endothermic peak characteristic of melting that shifts down from 256°C for PET to151°C for the copolyester containing 40%of CHD units.The additional low temperature melting peak found for both PET70CHD30and PET60CHD40has not a clear origin and it should be attributed to a second population of less perfect crystal-lites.The occurrence of a second crystalline form in these copolyesters is excludable since no new reflection was observed in their X-ray diffraction patterns.The melting enthalpy was observed to have a behavior paral-lel to that observed for the melting temperatures.It de-creases steadily with composition from51.3J gÀ1for PET98CHD2down to13.3J gÀ1for PET60CHD40.The fact that the copolyesters with low contents in CHD(less than10%)display in thefirst heating higher melting en-thalpy than PET could be simply due to differences in their preparation history.No melting peak was observedTable2Microstructure and crystal structure of the PETCHD copolyestersMicrostructure a X-ray diffractionPolyester Dyads(mol%)nl b Randomness Indexing c and d-spacings d(A˚)TT TCHD CHDCHD n T n CHD R0À110À10À111À1000À21 PET––––– 5.40(s) 5.06(s) 4.17(s) 3.47(m) 2.76(w) PET98CHD294.3 5.70.034.1 1.0 1.03nd nd nd nd nd(94.7)(5.2)(0.1)(37.1)(1.0)PET95CHD591.18.60.322.2 1.10.98 5.48(s) 5.15(s) 4.08(m) 3.47(s) 2.74(w)(90.5)(9.3)(0.2)(20.0)(1.1)PET90CHD1078.920.0 1.18.9 1.1 1.01 5.31(s) 5.00(s) 4.08(m) 3.54(m)–(80.8)(18.2)(1.0)(9.9)(1.1)PET80CHD2063.132.8 4.1 4.8 1.3 1.01nd nd nd nd nd(62.9)(32.8)(4.3)(4.8)(1.3)PET70CHD3048.742.39.0 3.3 1.4 1.01 5.31(s) 5.00(s) 4.08(m) 3.47(w)–(48.7)(42.2)(9.1)(3.3)(1.4)PET60CHD4036.446.117.5 2.6 1.80.96–––––a Experimental values obtained by means of the13C NMR data and Ref.[16].Theoretical values(in parentheses)were calculated on the basis of a Bernoullian dyad distribution using the copolyester composition data given in Table1.b Number average sequence lengths.c Indexing based on the triclinic lattice with parameters a0=4.56A˚;b0=5.94A˚;c0=10.75A˚;a=98.5°;b=118°;c=112°[17].d Intensities visually estimated and denoted as s=strong,m=medium,and w=weak;nd:not determined.1498N.Sa´nchez-Arrieta et al./European Polymer Journal41(2005)1493–1501for the PECHD homopolymer.On he other hand,onlycopolymers containing 10mole%as maximum of CHD units were found to be able to crystallize upon cooling.In these samples,the variation of both T m and D H m with composition followed the same trend as in pristine sam-ples although slightly lower values were found.This is an expected result usually obtained when samples crys-tallized from solution and from the melt are compared.For the determination of T g ,pristine polymer sam-ples were melted at 280°C and then rapidly quenched into liquid nitrogen.In general,all copolyesters showed a single T g with a value between those of the two homo-polymers PET and PECHD (82and 14°C,respectively),which steadily diminishes with the increase in the con-tent of CHD units.As expected,chain mobility in the amorphous phase appears to be less restricted when the rigid planar phenylene group is replaced by the cyclohexylene group.Nevertheless,it should be taken into account that the presence of relatively high amounts of DEG in the copolyesters must contribute significantly to depress the T g .This does not applies however to PECHD homopolymer,which distinguishes in showing a particularly low T g (14°C)whereas its content in DEG is relatively low and comparable to that found in PET.Tensile data,such as the Young Õs modulus (E ),the maximum tensile strength (r max ),and the elongation at break (e break )were measured for PET and for the copolyesters containing up to 30%of CHD units.Spec-imens were cut from amorphous films that were pre-pared by hot-pressing and subsequent quenching to room temperature.The numerical values of these mechanical parameters are listed in Table 3.It is ob-served that the Young Õs modulus increased significantly upon copolymerization and that the maximum tensilestress remained essentially unchanged or increased slightly.Conversely,a drastic decrease in the elongation at break took place with increased contents of the CHD units revealing the inability of these copolymers to be plastically deformed.4.ConclusionsThe polycondensation procedure used previously by us in the preparation of copolyesters of PET containing substituted isophthalate and terephthalate comonomers has proven to be effective also to obtain PET copolymers containing 1,4-cyclohexylene dicarboxylate units.The copolyesters have satisfactory molecular sizes,a random distribution of the diacidic comonomers along the chain for all compositions examined,and a cis –trans 1,4-cyclo-hexylene ratio of approximately 2:3.The effect of the replacement of the aromatic units by the cycloaliphatic units on structure and properties has been systematically studied and results can be summarized as follows:(a)Crystallinity of the PETCHD copolyesters decreases in overall with the content in cycloaliphatic units being still present in the copolyester containing 40mole%of such units.(b)The crystallizability of the PETCHD copoly-esters decreases with the content in cycloaliphatic units,to the point that only copolyesters containing less than 20mole%of such units are able to crystallize from the melt.(c)The monoclinic crystal structure of PET ap-pears to be preserved in all the semicrystalline copolyest-ers.(d)Both melt and glass transition temperatures decrease notably with copolymerization.(e)Copolyest-ers are more rigid and brittle than PET,a behavior that becomes more pronounced with the extent ofcopolymerization.Fig.5.Powder X-ray diffraction patterns of PET (a)and PET 70CHD 30(b).N.Sa ´nchez-Arrieta et al./European Polymer Journal 41(2005)1493–15011499AcknowledgmentsThis work has been supported by CICYT grant MAT2003-06955-CO2-01.Technical and additionalfinancial support received from Catalana de Polı´mers,S.A.(Barcelona,Spain),is also gratefully acknowledged.The assistance of Dr.J.Bou for GPC experiments is greatly appreciated.References[1]Tsutsumi N,Nagata M.In:Salamone JC,editor.Poly-meric materials encyclopedia.Boca Raton,FL:CRC;1996.p.6110–4.[2]Kint DPR,Mun ˜oz-Guerra S.Polym Int 2003;52:321.[3]Chong CT.Surf Coat Aust 1998;35:14.[4]Vanhaecht B,Teerenstra MN,Suwier DR,Willem R,Biesemans M,Koning CE.J Polym Sci A:Polym Chem 2001;39:833.[5]Zhang T,Xu M,Chen H,Yu X.J Appl Polym Sci 2002;83:2509.[6]Jackson Jr WJ,Darnell Patent 4327206,1982.[7]Jackson Jr WJ,Darnell Patent 4342862,1982.[8]Turner SR,Seymour RW,Dombroski JR.In:Scheirs J,Long TE,editors.Modern polyesters.Chichester:Wiley;2003.p.267–92.[9]Kricheldorf H,Schwarz G.Makromol Chem 1987;188:1281.[10]Kint DPR,Martı´nez de Ilarduya A,Mun ˜oz-Guerra S.J Polym Sci A:Polym Chem 2000;38:1934.[11]Kint DPR,Martı´nez de Ilarduya A,Mun ˜oz-Guerra S.J Polym Sci A:Polym Chem 2000;38:3761.[12]Kint DPR,Martı´nez de Ilarduya A,Mun ˜oz-Guerra S.J Polym Sci A:Polym Chem 2001;39:1994.[13]Moore WR,Sanderson D.Polymer 1968;3:153.[14]Fakirov S,Seganov I,Kurdowa E.Makromol Chem1981;182:185.[15]Yu T,Bu H,Chen J,Mei J,Hu J.Makromol Chem1986;187:2697.T a b l e 3T h e r m a l a n d m e c h a n i c a l p r o p e r t i e s o f P E T ,P E C H D a n d P E T C H D c o p o l y e s t e r sP o l y e s t e rD S CT G AT e n s i l e p r o p e r t i e s aF i r s t h e a t i n g bC o o l i n g b S e c o n d h e a t i n g b T d c (°C )T d s d (°C )R W e (%)E (M P a )r m a x (M P a )e b r e a k (%)f P E T 98C H D 27724051.315623.723226.539543218.81612(89)51.4(3.6)4.7(0.3)P E T 95C H D 57423347.315423.222827.439042619.51623(25)51.6(0.7)4.6(0.1)P E T 90C H D 107022445.37614.921821.9384428,43416.61757(34)46.6(1.5)3.3(0.2)P E T 80C H D 206219826.8––––387426,43317.11676(48)39.1(1.7)2.9(0.2)P E T 70C H D 305486,177g21.4––––385431,43614.41707(13)37.5(3.5)2.8(0.4)P E T 60C H D 404887,151g13.3––––392433,44212.7n d n d n d P E C H D14––––––394439,4456.5n dn dn daT h e s t a n d a r d d e v i a t i o n s a r e g i v e n i n p a r e n t h e s i s .bT h e m e l t i n g (T m )a n d c r y s t a l l i z a t i o n (T c )t e m p e r a t u r e s a n d t h e i r r e s p e c t i v e e n t h a l p i e s (D H m ,D H c )w e r e m e a s u r e d a t h e a t i n g /c o o l i n g r a t e s o f 10°C m i n À1.cT e m p e r a t u r e a t w h i c h a 10%w e i g h t l o s s w a s o b s e r v e d i n t h e T G A t r a c e s r e c o r d e d a t 10°C m i n À1.dT e m p e r a t u r e o f m a x i m u m d e g r a d a t i o n r a t e .eR e m a i n i n g w e i g h t a t 550°C .fT h e g l a s s -t r a n s i t i o n t e m p e r a t u r e w a s t a k e n a s t h e i n fle c t i o n p o i n t o f t h e h e a t i n g D S C t r a c e s o f m e l t -q u e n c h e d s a m p l e s r e c o r d e d a t 20°C m i n À1.gD o u b l e m e l t i n g p e a k .1500N.Sa´nchez-Arrieta et al./European Polymer Journal 41(2005)1493–1501。
天然药物化学-黄酮NMR
天然药物化学-黄酮NMR黄酮NMR检测摘要黄酮是天然产物中的重要类别，经常作为调节生物活性的有效化学物质。
NMR是分析天然产物结构的有效手段，它可以用于识别不同构型的结构信息和结构变化。
本文主要介绍了黄酮类化合物在NMR检测中的应用，包括核磁共振（NMR）技术的基本原理，NMR技术如何用于黄酮化合物的结构分析，如何利用NMR技术鉴定黄酮化合物的特征信息以及物质结构的变化。
关键词：黄酮；核磁共振；NMR检测；结构分析IntroductionNMR Basic PrincipleNMR is a spectroscopic technique used for studying the structure and dynamics of molecules. NMR is based on the fact that each type of element or isotope has a characteristic magnetic moment when exposed to an external magnetic field. When the external magnetic field is applied, the nuclei with spin on the axis may absorb or emit the energy from the external magnetic field, which is determined by the intensity and frequency of the magnetic field，and the structure of the molecule. This phenomenon can be used to analyze the structure and dynamics of molecules.NMR Application in Anthocyanin Structural AnalysisNMR has been widely used in the structural analysis of anthocyanins. In the spectra of anthocyanins, the most obvious signals are those of the most abundant C=C and C-O double bonds, which are responsible for the conjugation of the chromo- or anthocyanidins. The H-NMR signal of the C=C double bond is usually a multiplet, while the C-O double bond signal is a singlet. The 1H-NMR and 13C-NMR can also be used to determine the location of the OH group and the position of the glycosyl residues. In addition, the 3D-NMR technology can be used to determine the glycosylation pattern of the anthocyanins.Conclusion。
不对称催化自由基反应研究计划
不对称催化自由基反应研究计划(中英文实用版)Task Title: Research Plan on Asymmetric Catalytic Free Radical ReactionsTask Title: 不对称催化自由基反应研究计划Introduction:The research plan aims to explore the mechanisms and applications of asymmetric catalytic free radical reactions.These reactions have garnered significant attention due to their potential in synthetic chemistry, particularly in the creation of chiral molecules.介绍：该研究计划旨在探讨不对称催化自由基反应的机制和应用。
这些反应因其在合成化学中的潜力而受到广泛关注，尤其是在创建手性分子方面。
Objective 1: Mechanistic StudiesThe first objective is to conduct an in-depth investigation into the mechanisms of asymmetric catalytic free radical reactions.This will involve the use of various experimental techniques such as kinetic analysis, nuclear magnetic resonance (NMR), and electron paramagnetic resonance (EPR) spectroscopy.目标1：机理解析第一个目标是深入研究不对称催化自由基反应的机制。
introductiontoso...
One-DimensionalMetals Conjugated Poly-mers,Organic Crystals,Carbon Nanotubes.Von Siegmar Roth und David Carroll.Wiley-VCH,Weinheim 2004.251S.,geb., 119.00E.—ISBN 3-527-30749–4Vorliegend erscheint die zweite,überar-beitete und erweiterte Ausgabe eines Buchs,dessen Ursprünge in einem Vor-lesungsskript eines der Autoren liegen. Im Mittelpunkt des Interesses stehen physikalische Eigenschaften eindimen-sionaler organischer Leiter und deren Anwendungen.Der Text–mit Cartoons und Skizzen dekoriert–scheint in der Absicht verfasst,Einsteigern in das Gebiet ihre Berührungsängste mit der Thematik zu nehmen.Entsprechend sind die Ausführungen intuitiv und mit einem Minimum an mathematischen Ausdrücken versehen,wodurch der Stoff an vielen Stellen erfrischend leicht vermittelt wird.Ein Problem dieses Buches besteht darin,dass die avisierte Zielgruppe nicht immer klar zu erkennen ist.An manchen Stellen bemühen sich die Au-toren,die Themen und die zugrunde lie-genden Konzepte möglichst einfach zu erläutern,sodass Nichtspezialisten ohne viel physikalisches Grundwissen angesprochen scheinen.Andererseits werden in scheinbar zufälliger Folge stark fachsprachliche Passagen zwi-schengeschaltet,die nur für Fortge-schrittene verständlich sind.Neulinge auf dem Gebiet der eindimensionalen Metalle,die mit den Grundlagen der Festkörperphysik nicht vertraut sind,werden auf nützliche Erläuterungenstoßen,mehr noch aber auf fachlicheHürden.Versierte Leser andererseitswerden an einigen gescheiten Erläute-rungen Gefallen finden,dafür abereinen ausführlichen Literaturüberblickvermissen.Dass mathematische Glei-chungen sehr dünn gesät sind,machttrotz der stets souveränen Ausführun-gen eine rigorose Behandlung der The-matik unmöglich.Die Autoren sprechendiesen Punkt im Vorwort an und verwei-sen den Leser auf andere Quellen,manmuss sich allerdings fragen,ob dieserAnsatz effektiv ist.Die vorliegende zweite Ausgabewurde um aktuelle Themen wie licht-emittierende Materialien,Feldeffekt-transistoren und Kohlenstoffnanoröh-ren erweitert.Andere Schlüsselanwen-dungen wie Aktuatoren und Sensorensowie elektrochrome Eigenschaftenwerden nur in einem Absatz abgehan-delt,ohne Darstellung der Zukunfts-perspektiven und Beurteilung vonForschungsergebnissen.Bei diesenThemen bleibt das Buch hinter denErwartungen zurück.Enttäuschend an dem Buch sind dievielen chemischen Ungenauigkeiten.Mit Erstaunen ist zu sehen,dass dieStickstoffatome des auf dem Einbandabgebildeten Polypyrrols tetraedrischdargestellt sind.Angesichts der Bedeu-tung des p-Charakters des Stickstoff-Elektronenpaars für die Eigenschaftenvon Polypyrrol wäre hier mehr Sorgfaltangebracht gewesen.Es gibt eine be-trächliche Zahl an Abbildungen mit feh-lerhaften chemischen Strukturen.Mehr-fach findet man drei-und fünfbindigenKohlenstoff,zweibindigen Stickstoffsowie Radikale und Ionen mit wahllosoder falsch positionierten freien Elek-tronen und Ladungen.Bei den Struktu-ren der…Shish-Kebap“-Metallophthalo-cyanine hat man den Eindruck,die Me-tallatome seien durch Cl22À-Brückenverbunden.Der Jahn-Teller-Effekt wirderwähnt,die zur Veranschaulichung ge-dachte Abbildung macht jedoch keinenSinn.In Anbetracht der Tatsache,dassdie konstitutiven molekularen Eigen-schaften sehr oftüber die beschriebenenMaterialeigenschaften entscheiden,un-tergraben diese vielen Fehler zu einemgewissen Grad die Glaubwürdigkeitdes Textes.Eine Stärke des Buchs sind die intui-tiven Erläuterungen zu den Eigenschaf-ten eindimensionaler Materialien,diemit Gewinn auch in meine eigene Vorle-sung einfließen werden.Studierende,die sich ein fundiertes Grundwissenüber eindimensionale Metalle aneignenwollen,werden auf zusätzliche Texte zu-rückgreifen müssen,während aktiv For-schende,die nach einem Leitfaden aktu-eller Forschungsarbeiten suchen undgrundlegende Konzepte erläuterthaben möchten,an manchen Stellenfündig werden,aber auch einiges ver-missen dürften.Timothy M.SwagerDepartment of ChemistryMassachusetts Institute of TechnologyCambridge,MA(USA)Introduction to Solid-State NMRSpectroscopyVon Melinda J.Duer.BlackwellPublishing,Oxford2004.349S.,Broschur,29.99£.—ISBN1-4051-0919-9Die Festkörper-NMR-Spektroskopie istderzeit eine rasch wachsende Teildiszi-plin im Bereich der magnetischen Reso-nanzspektroskopie.Besonders im letz-ten Jahrzehnte haben methodische undinstrumentelle Verbesserungen sowieFortschritte in der Probenpräparationneue Möglichkeiten zur Untersuchungmolekularer Strukturen und ihrer Dyna-mik eröffnet.Die Bandbreite von An-wendungen reicht von der Biochemieüber die Materialwissenschaften bis hinzur Geologie.Wer sich für die Festkör-per-NMR-Spektroskopie interessierte,war lange Zeit auf die Standardwerkevon Mehring,Slichter und Ernst ange-wiesen,die alle theoretischen Grundla-gen liefern,leider aber nur einen be-AngewandteChemieBücher2527 Angew.Chem.2005,117,2527–2528www.angewandte.de 2005Wiley-VCH Verlag GmbH&Co.KGaA,Weinheimgrenzten Nutzen haben,wenn Anwen-dungen neuentwickelter Festkörper-NMR-Methoden gefragt sind.Das vorliegende Buch von Melinda J.Duer verschafft einenÜberblick über die theoretischen Grundlagen der Festkörper-NMR-Spektroskopie und diskutiert darüber hinaus viele der erst kürzlich entwickelten Methoden.Es ori-entiert sich an den ersten sechs Kapiteln des2002von der gleichen Autorin publi-zierten Buches Solid-State NMR Spec-troscopy:Principles and Applications.Das erste Kapitel widmet sich in erster Linie der quantenmechanischen Beschreibung von Festkörper-NMR-Ex-perimenten.Der Schwerpunkt liegt dabei auf Transformationen der Raum-und Spinkoordinaten,der wesentlichen Freiheitsgrade in einem anisotropen Medium.Themen wie die mehrdimen-sionale NMR-Spektroskopie,Phasen-zyklen und die phasenempfindliche Auf-nahme von2D-Spektren sind in den meisten einschlägigen Werken der (Flüssigkeits-)NMR-Spektroskopie be-schrieben und werden hier nur kurz an-gesprochen.Kapitel2gibt einenÜber-blicküber fast alle Basistechniken mo-derner Festkörper-NMR-Experimente, einschließlich Magic-Angle-Rotation sowie Entkopplungs-und Kreuzpolari-sationstechniken.Im Unterschied zum Vorgängerwerk werden auch praktischeDetails wie das Justieren des MagischenWinkels oder das Optimieren einesKreuzpolarisationsexperimentes be-schrieben.Solche Details sind inNMR-Nachschlagewerken sonst seltenzu finden und dürften besonders für un-erfahrene Anwender hilfreich sein.In den Kapiteln3–5werden die dreiHauptwechselwirkungen der Festkör-per-NMR-Spektroskopie–die chemi-sche Verschiebung,die dipolare Kopp-lung und die quadrupolare Kopplung–separat behandelt.Kapitelweise wird er-klärt,wie die betreffende Wechselwir-kung mithilfe kürzlich entwickelter Ex-perimente gemessen werden kann.Angeeigneter Stelle wird dabei immerwieder auf verwandte Forschungsgebie-te wie die Flüssigkeits-NMR-Spektro-skopie oder die Ab-initio-Quantenche-mie verwiesen.Kapitel6gibt schließlicheinen nützlichenÜberblicküber einennur scheinbar unwichtigen Aspekt derFestkörper-NMR-Spektroskopie,näm-lich die Erforschung der molekularenDynamik voll oder teilweise immobili-sierter Moleküle.Dem Buch gelingt ein guter Kom-promiss zwischen einer tiefschürfendenBehandlung der theoretischen Grundla-gen der Festkörper-NMR-Spektrosko-pie und einer Einführung in moderneMessmethoden.Als sehr hilfreich emp-fand ich die Verwendung grau unterleg-ter Bereiche zur Unterscheidung vonGrundlagentexten und tiefer gehenden,oftmals theoretischen Aspekten.Unklar bleibt hingegen,welche Bedeu-tung die am Ende der Kapitel aufgeführ-ten Notizen haben.Die meistenSchreibfehler aus dem Vorgängerwerkvon2002wurden berichtigt.Naturge-mäßkann ein als Einführung gedachterText nicht alle relevanten Technikender Festkörper-NMR-Spektroskopie an-gemessen abdecken,dennoch wäre eineDiskussion der in den Material-undBiowissenschaften zunehmend wichti-ger werdenden skalaren Kopplung(J-Kopplung)angebracht gewesen.Ebenso fehlt in Kapitel1eine zumindestkurze Einführung in Relaxationsvor-gänge.Davon abgesehen erhält derLeser einen hilfreichen und aktuellenÜberblicküber moderne Festkörper-NMR-Techniken für eine Vielzahl vonAnwendungen.Marc BaldusMax-Planck-Institutfür Biophysikalische ChemieGöttingenDOI:10.1002/ange.200485254Bücher2528 2005Wiley-VCH Verlag GmbH&Co.KGaA,Weinheim www.angewandte.de Angew.Chem.2005,117,2527–2528。
核磁共振设备迁移流程
核磁共振设备迁移流程(中英文版)Title: Nuclear Magnetic Resonance Equipment Relocation Process Title: 核磁共振设备迁移流程Introduction:Relocating nuclear magnetic resonance (NMR) equipment is a complex task that requires careful planning and execution to ensure the safety of the equipment and the technicians involved.This document outlines the step-by-step process for relocating NMR equipment, including preparing the new location, packing and transporting the equipment, and setting up the equipment in the new location.介绍：迁移核磁共振（NMR）设备是一项复杂任务，需要精心规划和管理以确保设备安全及技术人员的人身安全。
本文档概述了迁移NMR设备的分步流程，包括准备新位置、打包和运输设备以及在新位置安装设备。
Preparation:Before moving the NMR equipment, it is important to prepare the new location to ensure that it meets the necessary specifications.This includes ensuring that the floor can support the weight of the equipment, that there is proper ventilation, and that the electrical outlets are compatible with the equipment"s requirements.准备：在移动NMR设备之前，确保新位置符合必要规格非常重要。
NMR参数说明
OperatingtheBruker Avance DRX-400NMRWilliam D. Wheeler, Ph.D.Department of ChemistryUniversity of WyomingRevised September 7, 2006INTRODUCTIONThe procedures for the recording and processing of a routine proton or carbon NMR spectrum using a standard set of parameters are described here. The topics covered are:Starting the NMR ProgramSetting Up an ExperimentLoading, Locking and Shimming a SampleData AcquisitionData ProcessingExpanding the SpectrumThe XWinNMR ToolbarReferencing the SpectrumIntegrationPlottingExiting the programXWinNMR ParametersXWinNMR CommandsProbe Calibration ResultsSTATUS BARThe status bar at the bottom of the screen displays both a short description of the menu item highlighted and the status of a the current command.HELPThere is help available by choosing Help from the main menu and selecting either Contents or Index.STARTING THE NMR PROGRAMStarting XWinNMR.From the desktop, single click the XWinNMR icon.SETTING UP AN EXPERIMENTOpen a new file.NEW (or EDC)Create a new data set for your sample by typing new(or edc) at the XWinNMR command prompt. Thisfunction can also be accessed by choosing File andthen New... from the main menu bar.NAME name Enter a name for your data set. You can save severalNMR experiments (1H, 13C etc) for one compoundunder one name.EXPNO 1Enter an experiment number for your data set. This isa number between 1 and 998. You might use expno1 for 1H,2 (or 13) for 13C etc..PROCNO 1Enter a processing number for your data set (usually1). You can process your data several different waysand compare the results.DU /opt/xwinnmr The disk unit must always be /opt/xwinnmr.USER username Enter a username. This must be your user name (thename you used to log on with).TYPE The type must always be nmr[SAVE]Save the data set.Read a standard parameter file.RPAR Read in a standard parameter file by typing rpar at theXWinNMR command prompt. Pick “+proton” (or“+carbon”) from the list. Click the [Copy All] button toread in the parameters. The computer alphabetizesthe “+” sign before the letters, so that the standardfiles are at the top of the list. Note that parameterfiles also contain an entry for the solvent, and readinga parameter file after locking the sample may replacethe solvent parameter with an incorrect value.Editing acquisition parameters.ASED (or EDA)Edit the acquisition parameters. A listing of a few ofthe parameters and their meaning is shown below. Amore complete listing is included at the end of thisdocument. Note that the auto setup editor, ased,displays only the acquisition parameters relevant toyour experiment, while the edit acquisition parameterseditor, eda, displays all of the acquisition parameters.Both editors are useful.PULPROG zg PULse PROGram (experiment)TD32768number of Time Domain samples (real+imaginary)NS16Number of ScansSWH8000Sweep Width in HzSW20Sweep Width in ppmD[1] (or d1)3relaxation DelayLOADING, LOCKING AND SHIMMING A SAMPLELoading the sample.The following functions are carried out using the BOSS keyboard.[Lock On/Off]Turn the lock off. Press the [Lock On/Off] button.The light should change from on to off.[Lift On/Off]Eject the sample. Press the [Lift On/Off] button. Thelight should change from off to on).Replace the current sample with your own. Make sure that your sample spins freely in the “glass bearing” before inserting into the spinner. Carefully set the depth.[Lift On/Off]Load the sample. Press the [Lift On/Off button. Thelight should change from on to off.[Spin Rate]Adjust the spin rate. Use the knob to set the desiredvalue (usually 18 rps).Wait for the sample to spin. The light in the [Spin On/Off] button will blink until the set spinning speed is achieved, then stay on.Lock the sample.LOCK Lock your sample by typing lock at the commandprompt. Choose a solvent from the list. The [LockOn/Off] light will blink until the sample is locked, thenstay on.Automatic Shimming of the sample.TUNE QZ1Z2Shim your sample automatically by typing tune qz1z2(or tune sh12) at the command prompt. Wait for the“tuning” routine to finish.Manual Shimming of the sample.LOCKDISP Open the lock display window by typing lockdisp onthe command line. The light on the [FINE] button onthe BOSS keyboard should be lit. If it is not, press the[FINE] button to turn it on. To manually shim, pressthe [Z] button and then turn the knob until themaximum signal is obtained. Repeat for [Z2]. If thesignal goes off scale, press the [LOCK GAIN] buttonand adjust the gain with the knob until the signal isback on scale.DATA ACQUISITIONRGA Set the receiver gain. This will take a few seconds.ZG Start the acquisition.ACQU Open the acquisition window to display the FID as it isacquired. A dialog box in the upper right hand cornerof the window displays the number of scans acquiredso far, and the time remaining.DATA PROCESSINGLB Set the argument for exponential multiplication.EM Multiply the FID by an exponential with an argumentof LB.FT Fourier transform the spectrum.PK Phase this spectrum with a phase correctiondetermined in a previous experiment.APK Automatically phase correct the spectrum.Composite commands These“macros” execute multiple commands.EFP EM + FT + PK.FP FT + PK.ZGA ACQU + ZG.[phase]Clicking the [phase] button in the XWinNMR tool barwill cause the display to change to the phasecorrection window.Before phasing the spectrum, you should first define the phase pivot. The phase pivot is the point in the spectrum about which the first order phase correction is applied. The zero order correction is applied equally to the entire spectrum. The first order correction is zero at the phase pivot and increases for points farther and farther away. The [biggest] button will set the phase pivot to the position of the largest peak and attempt to phase the spectrum. The [cursor] button will allow you to define any point in the spectrum as the phase pivot. The phase pivot is marked on the display by a dashed vertical line. Phasing is accomplished by positioning the mouse cursor over the [PH0] button, holding the LEFT mouse button down, and then dragging the mouse. When you are satisfied with the phase correction, release the LEFT mouse button. Repeat for [PH1].When you are finished, press the [return] button. The pop up window gives you several choices. The cancel button returns you to the phase correction window. The Save & return button applies the phase correction to the spectrum and then returns you to the normal display window. The Save as 2D & return button also saves the phase correction to the most recently displayed 2D spectrum. The Return button returns you to the normal display window without applying the phase correction.EXPANDING THE SPECTRUMClicking the LEFT mouse button inside the spectral display will cause the cursor to change to a vertical arrow pointing down and it will track with the spectrum. As the mouse is moved back and forth, the cursor moves across the spectrum with it. A dialog box also appears in the upper right hand corner of the window and displays information about the cursor position. Clicking the MIDDLE mouse button will anchor a cursor at the current position. The dialog box now shows information about the cursor position with respect to the anchor point. Clicking the MIDDLE mouse button a second time causes the spectrum to be expanded between the two points. To turn the tracking cursor off, click the LEFT mouse buttom.THE XWinNMR TOOL BARThe left hand margin of the XWinNMR window has three columns ofbuttons that provide additional functionality to the program.The six buttons of the top two rows provide for vertical scaling.The [*2] [/2] and [*8] [/8] buttons increase or decrease thevertical scaling by 2 or 8. The right button on the top row resets the vertical scale so that the largest peak in the spectrum is displayed full scale. The right button on the second row is used to interactively set the vertical scaling. This is accomplished by placing the cursor over the button, holding down the left mouse button and then dragging the mouse (up and down) to adjust the scale.The next row of buttons are for horizontal scaling. The leftbutton expands the spectrum. The middle button contracts the spectrum and the right button resets the horizontal scale so that the complete spectrum is displayed.These buttons shift the spectrum vertically. The left buttonmoves the baseline of the spectrum to the middle of the screen. The middle button moves the baseline of the spectrum to the bottom of the screen. The right button is used to interactively set the vertical shift. This is accomplished by placing the cursor over the button, holding down the left mouse button and then dragging the mouse (up and down) to adjust the scale.These buttons shift the spectrum horizontally. The left buttonshifts the spectrum to the left. The middle button shifts the spectrum to the right.The plot buttons are used to define and display a plot region.The [dp1] button is the most commonly used to define a plotregion. The [PlotReg] button forces the program to display theportion of the spectrum defined as the plot region.These buttons affect the display. The [Y] button toggles thedisplay of the y scale. [YU] toggles the units of the y scale. [dot]displays the spectrum as dots. [Re] and [Im] display the real orimaginary parts of the spectrum. [fid] displays the free inductiondecay. [Sh] and [Ush] shuffle and un-shuffle the real and imaginary parts of the spectrum.This button sets the spectrometer frequency and sweep widthto match the values of the display.REFERENCING THE SPECTRUM[calibrate]Clicking the [calibrate] button will cause the display tochange to the calibration window.Upon entering the calibration window, there will be a cursor (vertical arrow pointing down) tracking the spectrum. As the mouse is moved back and forth, the cursor moves across the spectrum with it. Position the cursor at the reference point and click the MIDDLE mouse button. Type in the value of the reference and then press the Enter key.INTEGRATIONABS Apply an automatic baseline correction followed by anautomatic integration. To see the results of theintegration, type xwinplot, xwp or view.[integrate]Clicking the [integrate] button will cause the display tochange to the manual integration window.Integration is performed in a manner similar to expanding the spectrum. Click the LEFT mouse button. Move the cursor to the left of the region to be integrated. Click the MIDDLE mouse button. Move the cursor to the right of the region to be integrated. Click the MIDDLE mouse button. The integral will be displayed. Move the cursor to the left of the next region to be integrated ...When you are finished, click [return]. The pop up window gives you several choices. The CANCEL button returns you to the integration window. The “Save as ‘intrng’ & return” button, saves the integrations with the spectrum and then returns you to the normal display window. The Return button returns you to the normal display window without applying the integrations.PLOTTINGSETTI Set the title for the spectrum. This command starts atext editor. Enter a title to go with your spectrum.The title can have multiple lines, and each line will becentered in the spectral window of the plot.[dp1]Define a plot region. You can either enter a chemicalshift range to be plotted, or set the range to coincidewith the range displayed on the screen by answeringthe questions with “Enter”.XWP or VIEW Display the spectrum as it will be plotted on the paper. File / Print Plot the spectrum along with the title, parameters, andintegration.File / Close Close the xwinplot program.EXITING THE PROGRAMIMPORTANT: You must exit XWinNMR before logging out. If you do not, the next user will NOT be able to use the instrument.[quit]If the lock display window is open, close it by pressingthe [quit] button.EXIT Exit XWinNMR. This function can also be accessedby choosing File and then Exit from the main menubar.[OK]Answer “Do you really want to leave the program?”with [OK].[OK]If you get the “Process still active” dialog box, (insteadof the “Do you really want to leave the program?”dialog box), answer with [OK]. This message usuallymeans that the lock display window is still open.XWinNMR ParametersFile ParametersNAME data set NAMEEXPNO EXPeriment Number (1-998, 999 is used internally)PROCNO PROCessing Number (1-998)DU Disk Unit. (this must always be /opt/xwinnmr)USER your USER name (the name you used to login)TYPE this must always be nmr!Note:The raw data is saved in the directory/DU/data/USER/nmr/NAME/EXPNOAcquisition ParametersTD number of Time Domain samples (real+imaginary)NS Number of Scans (number of acquisitions to be averaged)DS number of Dummy ScansSWH Sweep Width in HzSW Sweep Width in ppmAQ AcQuisition time (calculated from TD and SW)D[1] (or d1)Delay 1 (usually the relaxation delay)P[1] (or p1)Pulse 1 (usually the length of the transmitter pulse)FIDRES temporal resolution of the FIDDW DWell time (sampling interval, 1/SW or 1/2SW)SOLVENT SolventO1P Offset 1 from the base frequency in Ppm (center of the spectrum) PULPROG PULse PROGram (experiment)PL[1] (or pl1)Power Level 1 (attenuation, larger #’s => lower power)XWinNMR ParametersProcessing ParametersSI SIze of the data in the frequency domain (usually TD/2)LB Line Broadening (used by EM, usually 0.1 for 1H)GB Gaussian Broadening (used by GM)TM1Trapezoid point 1 [range 0.0 - 1.0, usually 0.0] (used by TM)TM2Trapezoid point 2 [range 0.0 - 1.0, usually 0.1, {1.0 - TM2 used}] PHC0Zero order phase correction in degreesPHC1First order phase correction in degreesXWinNMR CommandsFile CommandsNEW create a NEW data set (EDC also works)Lock CommandsLOCK solvent LOCK the sample using parameters for solvent specified LOCKDISP LOCK DISPlay (displays lock signal as a function of time)RSH Read in a SHim file.Acquisition CommandsEDA EDit Acquisition parameters (displays all acquisition parameters) ASED Auto Setup Editor (displays only the acquisition parameters used for this experiment)RGA automatically adjust the Receiver GAinZG Zero Go, start accumulationACQU display the ACQUisition window (shows data as it is collected) TR TRansfer data from the spectrometer to the computerXWinNMR CommandsEXPT estimates the amount of EXPeriment TimeEDHEAD EDit the information for the probe HEADProcessing CommandsTM Trapezoid Multiplication (uses TM1, TM2)EM Exponential Multiplication (uses LB)GM Gaussian Multiplication (uses GB)WINFUNC interactively adjust WINdow FUNCtion parameters (LB, GB, etc.) FT Fourier transform the dataPK Phase the spectrum using previous values of PH0, PH1APK Automatically Phase the spectrumFP same as Ft + PkEFP same as Em + Ft + PkEDP EDit Processing parametersAnalysis CommandsSREF automatically Set the REFerenceABS Automatic Baseline Subtraction (and integration)Plot CommandsEDG EDit Plot parametersSETTI SET (edit) the TItle of the spectrumXWINPLOT Starts the xwinplot program.MacrosVIEW Executes the xwinplot command.ZGA Executes the commands ACQU + ZG.PROBE CALIBRATION RESULTSProbe Nucleus 90º PW(: Sec)PowerLevel(dB)90º Dec(: Sec)PowerLevel(dB)5 mm QNP 1H/13C/31P/19F1H11.3-6.0100.016.0 Z-gradient (#07)13C 6.0-6.060.015.031P 5.6-3.019F14.5-6.05 mm Multinuclear (#09)1H14.20.0100.018.513C9.30.031P 6.90.015N11.9-6.05 mm Multinuclear Inverse 1H7.4-3.0XYZ-gradient (#11)13C14.0-3.0100.014.031P15N(25.5)-3.0PARAMETERS FOR COMMON 1D EXPERIMENTSExperiment SettingHomonuclear Decoupling (zghd)pl24 = 40 - 50 dBDIGMOD = homodecoupling-digitalSet O2 for frequency of peak to be decoupledSet NUC2 to 1H (edasp) Presaturation (zgpr)pl9 = 40 - 50 dBd1 = 2.0 secSet O1 for frequency of the solvent peak。
- 1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
- 2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
- 3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。
-
the equilibrium constant K can be calculated from the signal integrals of the two signals.
(n
Fast and Slow Exchange The topic is often introduced with a discussion of a simple two-site exchanging system, for example, the methyl groups in dimethylformamide.
n -'- 6, - a,
(12)
LHl0 = 0 . 1
we can use the observed chemical shift 6 (with 6 h and 6, from slow-exchange measurements and the known values of [HI, and [GIo)to calculate K from eq 11. The observed chemical shift under fast-exchange conditions is a complicated function of [HI,, [GIo,ah, 6,. and K.
(slow exchange)
and where nhisthe mole fraction of uncomplexed host and n, is the mole fraction of complexed host. To use NMR methods to study such complexation phenomena, a t least one site (i.e., nucleus) in the uncomplexed host (or guest) molecule must give rise to a signal at chemical shift 6 h that is significantly different from the same site in the complexed host (or guest) molecule (6,). The magnitude of this difference (A6 = Zh - 8J often gives information about the structure of the complex, and may be as large as several ppm ( 7 ) .
Journal of Chemical Education
True K
1.00
(
R
'"
2.00 3.00
Table 1. Nonlinear Curving-Fining of Equation 12 to Find Kand 6~
Initial estimate o f K = 100 Initial estimate of K = 0.01
where [HI. and [GI. are the formal (i.e., initial) concentrations of host and guest ([C].= 0). The relative signal integrals at 61, and 6, give
I, --
l,+lh -%
K = 0.1/0.5/1.0
AND
[CI = n,[Hlo
(10)
Thus, eq 8 can be rewritten as
K=
nJ% (1 - nJ(R - nJ
(11)
where R is the ratio [GIJHI,. Determining Kunder Conditions of Fast Exchange How do we determine the value ofKunder fast-exchange conditions? We can rewrite eqs 1 4 , substituting h for a, and c forb. Then, due to the relationship 6,-s
6=n , S ,
+ (1- n,)Sb = n,(A6) + 6b
(2)
Thus, I t is stated that under "slow-exchange" conditions the spectrum consists of two signals: one for species A a t chemical shift 6. and one for species B a t 66. By contrast, under "fast-exchange" conditions there is just one signal at the population-averaged chemical shift. S = n,6, + nb& (fast exchange) (1) where n represents the mole fraction. In this context, "slow exchange" means that the differ, - fib, exence in chemical shift between A and B, AS = 8 pressed in Hz, is much larger than the rate constant for interconversion k = kl + k-, in Hz. Conversely, fast exchange means thatk >> A6 (1). By measuring the spectrum under slow-exchange conditions (e.g., at sufficiently low temperature), it is usually possible to determine both 8, and tibdirectly. Furthermore, and
nb So-6
K=-=n . S - Sb
(fmt exchange)
(5)
Complexation One of the most active areas in modern chemical research involves "molecular recognition", the formation of so-called host-guest (or H-G) complexes (C).
Figure 3. The effect o f dilution on a solution initially with [HI, [GI, = 1.0 M. Input parameters are K = 10 M', 8h = 0 Hz,6,= 10 Hz; output from eq 14.
An Introduction to NMR Titration for Studying Rapid Reversible Complexation
Roger S. Macomber University of Cincinnati, Cincinnati, OH 45221-0172
Nuclear magnetic resonance (NMR) spectroscopy is one of the most useful techniques available to chemists for the investieation of dvnamic molecular Drocesses. Most basic treatments of NMR include at least a qualitative description of the effect of "exchanre". - . that is. rcvcrsiblc dvnamlc processes, on the appearance of NMR spectra (I).
8 =8 .
- [$](b - m)
(fast exchange)
(13)
where
Figure 2. Same as Figure 1, extended to larger values of R.
376
The derivation of this expression is given in Appendix 1. Equation 1 3 describes the complexation-induced shift (CIS) of an NMR signal. The variation of 6 with changing R forms the basis of a general technique known as NMR titration (2-9) for the determjnation of K values.
Volume 69 Number 5 May 1992
375
.
I
YI
-I0 = 0 . 1
a
=r
DILUTION CURVE V/
1-18
& INITIAL
[GI0 = [HI0 = 1 .0
^
<
Figure 1. Plots of eq 13 relating S to R = [G]d[H],The values for,Kare (A)0.10; (B) 0.50; (C) 1.0; (D) 5.0; (E) 10; (F) 50; (G) I00 M- . For each line, [HI,= 0.10 M,6,= 0 Hz, and a,= 10 Hz.