大学有机化学课件24_15

500
1H NMR
Hydroxyl proton of OH group lies between alcohols and carboxylic acids; range is ca. d 4-12 ppm (depends on concentration). For p-cresol the OH proton appears at d 5.1 ppm (Figure 24.4).
Figure 24.3: Infrared Spectrum of p-Cresol
CH3Βιβλιοθήκη Baidu
C—H OH
O—H
C—O
3500
3000 2500 2000 1500
Wave number, cm-1
1000
Francis A. Carey, Organic Chemistry, Fourth Edition. Copyright © 2000 The McGraw-Hill Companies, Inc. All rights reserved.
121.7
Oxygen of hydroxyl group deshields carbon to which it is directly attached.
The most shielded carbons of the ring are those that are ortho and para to the oxygen.
Section 24.15 Spectroscopic Analysis of Phenols
Infrared Spectroscopy
infrared spectra of phenols combine features of alcohols and aromatic compounds
O—H stretch analogous to alcohols near 3600 cm-1 C—O stretch at 1200-1250 cm-1
Mass Spectrometry
Prominent peak for molecular ion. Most intense peak in phenol is for molecular ion.
•+ OH
••
m/z 94
UV-VIS
Oxygen substitution on ring shifts lmax to longer wavelength; effect is greater in phenoxide ion.
OH
O–
lmax 204 nm 256 nm
lmax 210 nm 270 nm
lmax 235 nm 287 nm
H
H
HO H
CH3 H
Figure 24.4 (page 961)
H
H
HO H
CH3 H
10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0
Chemical shift (d, ppm)
13C NMR
OH
155.1
112..3
116.1
129.4
139.8
CH3 21.3