波谱分析读书笔记

第五章色谱和光谱——化合物的纯化和结构研究方法重点讲授内容一、纯化方法、色谱技术简介二、质谱三、红外光谱四、紫外光谱五、核磁共振推荐参考书：1、宁永成编著，《有机化合物结构鉴定与有机波谱学》，科学出版社，20012、谢晶曦编著，《红外光谱在有机化学和药物化学中的应用》，科学出版社，19873、陈耀祖编著，《有机分析》Purification---- is a separation process which depends on the differential distributions of the components of a mixture between a mobile bulk phase and an essentially thin film stationary phase.Structure DeterminationPhysical properties Spectroscopic Methods---- Melting Point ---- IR (Infrared Spectroscopy)---- Boiling Point ---- NMR (Nuclear Magnetic resonance) ---- Specific Rotation ---- MS (Mass Spectrum)---- Refractive Index ---- UV (Ultraviolet Spectrum)有机波谱法（质谱、红外光谱、紫外光谱、核磁共振谱）波谱法特点(1) 样品用量少，一般来说2~3mg即可（最低可少到<1mg）；(2) 除质谱外，其它方法无样品消耗，可回收再使用；(3) 省时、简便(4) 配合元素分析（或高分辨质谱），可以准确地确定化合物的结构实例——分子式为C8H10的化合物可能结构：( 配四种异构体的核磁共振氢谱、红外光谱、紫外光谱图)一、 质谱——确定分子量、分子式，了解分子内原子连接的详细情况 1、 基本原理In a technique called mass spectroscopy, a molecule is vaporized and then ionized byremoving an electron. This produced a molecular ion, which is a radical cation, a species with an unpaired electron and a positive charge. Because of possessing high energy, the molecular ion may break apart into cations, radicals, neutral molecules, and other radical cations.M molecule+e molecular ion a radical cationelectronFragments（插入仪器工作原理图及质谱图样式）The analyzer tube is surrounded by a magnet. Its magnetic field deflects the positively charged fragments in a curved path. At a given magnetic field strength, the radius of the path traveled by a fragment, depends on its mass-to-charge ratio (m/z). The smaller the m/z of the fragment, the more the magnet deflects it. If a fragment’s path matches the curvature of the analyzer tube, the fragment will pass through the tube and out the ion exit slit. A collector records the relative number of fragments with a particular m/z passing through the slit. The more stable the fragment, the more likely it will make it to the collector. By slowly increasing the strength of the magnetic field, fragments with progressively larger values of m/z can be guided through the tube and out the exit slit.2、分子量、分子式的确定Molecular ion ---- the m/z value of the molecular ion gives the molecular weight of the compoundBase peak ---- is the one with the greatest intensity. ( it is assigned a relative intensity of 100% )M+1 peak or M+2 peak ---- often occurs because there are naturally isotopes of carbon, or other atomse.g. 1. The mass spectrum of an unknown compound has a molecular ion with a relative intensity of 43.27%, and an M+1 peak with a relative intensity of 3.81%. How many carbon atoms are in the compound?Solution: There are two naturally isotopes of carbon: 98.89% 12C and 1.11% 13CRelative intensity of M+1 peak 3.81Number of carbon atoms = = = 80.011 x (relative intensity of M peak) 0.011 x 43.27Table 5.1 The Natural Abundance of Isotopes Commonly Found in Organic CompoundsHigh-Resolution Mass Spectrometry can determine the exact molecular mass of a fragment with a precision of 0.0001 amu.e. g. Some compounds with a nominal molecular mass of 122 amu and their exact molecular massesMolecular Formula C9H14C7H10N2C8H10O C7H6O2C4H10O4C4H10S2 Exact Molecular Mass (amu) 122.1096 122.0845 122.0732 122.0368 122.0579 122.0225 e. g. Which molecular formula has an exact mass of 86.1096 amu: C6H14C4H10N2C4H6O2T able 5.2 The exact Masses of Some Common Isotopes3、分子离子峰的断裂规律与分子内原子连接情况（只要求掌握最基本的一些规律，参阅教材）1）产生氮正离子、氧正离子、卤正离子的裂解：α-裂解、β-裂解2）产生碳正离子的裂解：3）脱去中性分子的裂解烃类和卤代烃：CH 3CH 2CH 2CH 2CH 3CH 3CH 2CH 2+ CH 3CH 2CH 3CH 2CH 2+ CH 3CH 2m/z = 43m/z = 29CH 3CH 2CH 2CH 2+ CH 3m/z = 57CH 3CH 2CH 2CH 2+ CH 3m/z = 15molecular ion m/z = 72 CH 2CH 3+CH 2CH 3m/z = 69H 3CC HCH 3H 3CC H CH 335ClH 3CC H CH 337H 3C H 3CHm/z =78m/z = 80H 3CCHCH 3+ Clm/z = 43CH 3CH 2=35Cl CH 3CH 2=37Cl + CH 3m/z = 63, 65醇醚的β-裂解：OOOm/z = 101m/z = 101m/z = 87CH 3CH 2CH 2CH 2CH=OH + CH 3CH=OHm/z = 87m/z = 45对于第四个裂解方程式，请表示出两种碎片离子的形成过程，并写出各自丢失的片段。

二、 红外光谱——反映分子中键的振动能级的变化情况，提供官能团的信息1、 红外光谱基本原理——红外吸收光谱与化合物结构特征关系 A 、 常见的键的振动方式： 伸缩振动Stretching Vibrations ，symmetric stretchasymmetric stretch弯曲振动Bending Vibrations （面内、面外）s y m m e t r i c i n -p l n e b e n d (s c i s s o r )a s y m m e t r i c i n -p l ab e n d (r oc k ) u t -o f -p l a n e b e nd (t w i s t )a s y m me t r i c o u t -of -p l a n eb e n d (w a g )一个官能团由于有多种振动方式，在红外光谱中将有一组相应的吸收峰B、伸缩振动频率与成键原子质量、键的强度（键能、键长）的关系Hooke 定律：v~其中m1 m2m1+m2为折合质量振动频率与成键原子折合质量倒数的平方根成正比，即原子质量愈轻，振动频率愈高；与键的力常数的平方根成反比，即键能愈大，键长愈短，键的力常数愈大，振动频率愈高。