143 nfrared spectroscopy红外 光谱 Organic compounds also absorb electromagnetic energy in the infrared (R) region of the spectrum Infrared radiation does not have sufficient energy to cause the excitation of electrons but it does cause atoms and groups of atoms of organic compounds to vibrate faster about the covalent bonds that connect them These vibrations are quantized(量子化 And as they occur, the compounds absorb IR energy in particular regions of the
14.3 Infrared spectroscopy红外 光谱 Organic compounds also absorb electromagnetic energy in the infrared (IR) region of the spectrum. Infrared radiation does not have sufficient energy to cause the excitation of electrons, but it does cause atoms and groups of atoms of organic compounds to vibrate faster about the covalent bonds that connect them. These vibrations are quantized (量子化）. And as they occur, the compounds absorb IR energy in particular regions of the spectrum
Infrared spectrometers operate in a manner similar to that of visible -UV spectrometers. a beam of IR radiation is passed through the sample and is constantly compared with a reference beam as the frequency of the incident radiation is varied. The spectrometer plots the results as a graph showing absorption versus frequency or wavelength The location of an IR absorption band ( or peak can be showed representation of avenu waverurnber
Infrared spectrometers operate in a manner similar to that of visible-UV spectrometers. A beam of IR radiation is passed through the sample and is constantly compared with a reference beam as the frequency of the incident radiation is varied. The spectrometer plots the results as a graph showing absorption versus frequency or wavelength The location of an IR absorption band (or peak) can be showed representation of wavenumber V = λ 1 - Wavenumber 波 数 ;
R的产生与分子结构的关系 IR光谱又称为振动光谱
IR的产生与分子结构的关系 IR光谱又称为振动光谱 分 子 振 动 伸 缩 振 动 弯 曲 振 动 Molecules vibration 对 称 伸 缩 振 动 不 对 称 伸 缩 振 动 Symmetric stretching Asymmetric stretching H H H H Stretching vibration Bending vibration 面 内 弯 曲 振 动 面 外 弯 曲 振 动 An in-plan bending vibration An out-of-plane bending vibration H H H H
he frequency of a given stretching vibration and thus its location in an IR spectrum can be related to two factors these are the masses of the bonded atoms- -light atoms vibrate at higher frequencies than heavier ones and the relative stiffness of the 原子的质量越小,则剔频率越高,吸收峰将出 现在高波数区,相反,吸收峰则出现低波数区
The frequency of a given stretching vibration and thus its location in an IR spectrum can be related to two factors. These are the masses of the bonded atoms-- -light atoms vibrate at higher frequencies than heavier ones--- and the relative stiffness of the bond. 原子的质量越小，则振动频率越高，吸收峰将出 现在高波数区，相反， 吸收峰则出现低波数区
The stretching frequencies of groups
The stretching frequencies of groups Group Bond Frequency Range (cm-1 ) Alkyl C-H 2853-2962 Alcohol O-H 3590-3650 Amine N-H 3300-3500 Double bond Triple bond 1620-1680 2100-2260 Carbonyl group C O 1630-1780 C N 2220-2260