IR3

Example 1
Example 2
Example 3
Example 4
Example 5
Example 6
Example 7
Example 8
Example 9
Example 10
Example 11
Problem 1
Problem 2
Problem 3
Problem 4
main characteristic absorption bands, say less than five? Are some of the bands broad?
Step 2: Testing for Organics and

Hydrocarbons – Absorptions in the Region 3200–2700 cm-1 Are there absorptions above 3000 cm-1? Is the main absorption below 3000 cm-1? If the main absorptions are approximately 2935 and 2860 cm-1, and there are also absorptions at 1470 and 720 cm-1, then the compound probably contains a long linear aliphatic chain.
红外光谱
Infrared Spectroscopy
红外光谱的解析
红外光谱的六个区域
4000~2500 cm-1 ; 2500~2000 cm-1 ; 2000~1500 cm-1 ; 1500~1300 cm-1 ; 1300~910 cm-1 ; 910 cm-1 以下
1. 4000~2500 cm-1 X―H的伸缩振动区域。X = C，N，S， O等。P、Si、B等低于2500 cm-1 应注意水的吸收峰 2. 2500~2000 cm-1 三键和累积双键（─C≡C─、─C≡N─、 ─C═C═C─、─N═C═O、─N═C═S等）的 伸缩振动区Step 3: Testing for Hydroxy or Amino Groups
– Absorptions in the Region 3650–3250 cm-1 Is the main absorption band in the area broad?
The C-H stretch of a terminal alkyneexhibits a
3. 2000~1500 cm-1
双键的伸缩振动区域。红外谱图中很重 要的区域。 羰基化合物在~1650 ─ 1900 cm-1；烯基 氢面外弯曲振动的倍频~1600 ─ 2000 cm-1； 苯环的骨架振动在~1500、~1580、~1600 cm-1；C═C的伸缩振动~1620 ─ 1680 cm-1； C═N的伸缩振动~1640 ─ 1690 cm-1；N═O 的伸缩振动~1500 ─ 1600 cm-1；─NO2有对 称、不对称两种伸缩振动，不对称伸缩振 动在此区域。
Step 6: Testing for Aromatics – Well-defined
Absorptions in the Region 1615–1495 cm-1 typically two, sets of bands in the region, with one set around 1600 cm-1 and the other around 1500 cm-1, are consistent with an aromatic compound. Sometimes the absorptions occur as single bands, at other times one or more of the band sets may appear split, as an asymmetric doublet. This assignment is usually confirmed by the presence of other bands in the spectrum.
relatively narrow absorption at 3300 cm-1, and is associated with a second (C≡C) band at 2200 cm-1.
Step 4: Testing for Carbonyl Compounds –
Absorptions in the Region 1850–1650 cm-1 Is the absorption at the high end of the range, e.g. 1775 cm-1 or above? Is the absorption in the middle of the range, 1750–1700 cm-1? Is the absorption at the low end of the range, e.g. below 1700 cm-1?
Problem 5
Problem 6
Problem 7
Step 5: Testing for Unsaturation – Weak to
Moderate Absorption in the Region 1670–1620 cm-1 A relatively narrow, weak-to-moderate absorption, normally centered around 1650 cm-1, is indicative of olefinic unsaturation (C=C).
红外光谱的解析步骤
计算分子的不饱和度，根据不饱和度的
结果推断分子中可能存在的官能团。 根据吸收峰的位置、强度、形状分析各 种官能团及其相对关系，推出化合物的 化学结构
A Quick Diagnostic Assessment of an Infrared Spectrum
Step 1: Overall Spectrum Appearance Is the spectrum simple? Are there only a few
4. 1500~1300 cm-1
主要提供了C─H的弯曲振动的信息。甲 基在~1380、1460 cm-1同时有吸收，发生分 叉时表示有偕二（三）甲基的存在。 ─NO2的对称伸缩振动在此区域。
5. 1300~910 cm-1
所有单键的伸缩振动频率、分子骨架振 动频率都在这个区域。部分含氢基团的一 些弯曲振动和一些含重原子的双键（P═O， P═S等）的伸缩振动频率也在这个区域。这 个区域的红外吸收频率信息十分丰富，但 特征性不强。 6. 910 cm-1以下 苯环由于取代而产生的吸收（910~650 cm-1）是这个区域的重要内容。是判断苯环 取代位置的主要依据。另外烯的碳氢弯曲 振动频率处于本区及前一区，可用于判断 双键的类型。
Step 7: Testing for Multiple Bonding–
Absorption in the Region 2300–1990 cm-1 Multiply bonded nitrogen compounds and cumulated multiple bond compounds, such as cyanides (nitriles), cyanates, isocyanates, thiocyanates, and diazo compounds, exhibit characteristic absorptions in the region 2300– 1990 cm-1.
红外光谱的解析要点




1. 三要素：位置、强度、峰形 2. 同一基团的几种振动的相关峰是同时 存在的 3. 解析顺序: 先官能团区, 后指纹区 4. 标准红外谱图的应用: 如 Sadtler 谱图 集
红外光谱的解析步骤
化合物类型的判断
有机物和无机物 饱和化合物与不饱和化合物 烯烃或芳烃 推断可能含有的功能团 先看特征频率区（4000-1300），再 看指纹区（1300-400）。 先看强峰，再看弱峰 先找特征吸收峰，再找相关峰佐证