化学专业英语infraredspectroscopy课件.pptx（纯ppt,无音视频）

1、1Infrared SpectroscopyDetermining the structure of an organic molecule was a difficult and time-consuming process in the nineteenth and early twentieth centuries,but extraordinary advances have been made in the past few decades.Powerful techniques and specialized instruments that greatly simplify st

2、ructure determination are now available.Infrared(IR)spectroscopy is a method of structure determination that depends on the interaction of molecules with infrared radiant energy.Before beginning a study of infrared spectroscopy,however,we need to look into the nature of radiant energy and the electr

3、omagnetic spectrum.Electromagnetic SpectrumVisible light,X-rays,microwaves,radio waves,and so forth,are all different kinds of electromagnetic radiation.Collectively,they make up the electromagnetic spectrum.The electromagnetic spectrum is loosely divided into regions,with the familiar visible regio

4、n accounting for only a small portion of the overall spectrum,from 3.8 x 107 to 7.8 x l07 m in wavelength.The visible region is flanked by the infrared and ultraviolet regions.That part of the electromagnetic spectrum of longer wavelength than the visible region and shorter wavelength than the micro

5、wave region is known as the infrared region.比可见光区域更长的那部分电磁波谱和比微波区域更短的那部分波长区域，被称为红外区域。4However,the decidedly limited portion of the infrared region which lies between wavelengths of 2.5 and 15 or between frequencies of 4000 cm-1 and 660 cm-1 is of greatest practical use to the organic chemist.然而，位于波长

6、的 2.5 至15 或频率在4000 cm-1和660 cm-1之间的红外区域的绝对有限的部分是有机化学家最大的实际使用区域之一。5Radiation energy is this region may be absorbed by an organic molecule and converted into molecular vibrational energy.在这一区域的辐射能量可以由一个有机分子吸收 并转换成分子振动能量。6Organic molecules undergo continual stretching,bending,and rotational motions,and

7、,when the frequency of the infrared light passing through an organic compound corresponds to the frequency of one the molecular motions cited above,the light is absorbed.有机分子在做不断的拉伸、弯曲、和旋转运动，当有机化合物的红外光通过的频率对应于上述的分子运动频率时，光线被吸收。红外光谱是由于分子的振动能级的跃迁（同时伴随着转动能级的跃迁）而产生的。当用一定频率的红外光照射物质时，若物质的分子中某基团的振动频率与之相同时，则

8、物质就能吸收此种红外光。红外光谱原理8One restriction of the above discussion is worthy of mention,namely,the stretching or bending motion of atoms within a molecule must cause a change in the instantaneous dipole moment in order to produce an absorption peak in the infrared spectrum.上述讨论的一个限制是值得一提的，即一个分子内的原子拉伸或弯曲的运动必

9、须引起瞬时偶极矩的变化，以产生红外光谱吸收峰。Symmetricalstretching对称伸缩对称伸缩Antisymmetricalstretching非对称伸非对称伸缩缩Scissoring剪刀式摆剪刀式摆动动 RockingWaggingTwisting 左右摇摆左右摇摆上下摇摆上下摇摆扭摆扭摆10 Of even greater usefulness to the organic chemist is the fact that certain groups of atoms(certain functional groups)give rise to stretching or be

10、nding vibrational absorption bands at or near the same wavelength,regardless of the structure of the remainder of the molecule.不管其分子的其余部分结构如何，一些原子组（官能团）在相同或接近相同波长产生的伸缩和变形振动吸收带，对有机化学有较大用处。11Thus,it is frequently possible for an experienced chemist to examine the infrared spectrum of an unknown compou

11、nd and decide what functional groups are present in the molecule,even though he might not have any other information about the compound whatsoever.因此，一个经验丰富的化学家往往可以测定一个未知化合物的红外光谱，并决定分子中可能存在的官能团组别。即使他可能不会有这个化合物的任何其他信息。12The literature on the subject of the correlation of structure with infrared absor

12、ption spectra is vast,and no attempt will be made here to give complete details.涉及结构与红外吸收谱关系的文献很多，这里不试图给出全部细节。Introduction to various types of organic compounds characteristic absorption AlkaneThe infrared spectrum of methyl cyclohexaneC-H伸缩振动伸缩振动3000cm-1 C-H弯曲振动弯曲振动有机物的命名烷烃（alkanes）直链烷烃类化合物的命名是有机命名

13、的基础。英文名称除了含1到4个碳原子以外，其余均用希腊文和拉丁文的数词加上相应的词尾（-ane）来命名，10个碳原子以上的则在数词前加前缀un、do、tri、tetra、penta等。如：甲烷 methane 乙烷 ethane 丙烷 propane 丁烷 butane 戊烷 pentane 己烷 hexane 庚烷 heptane 辛烷 octane 壬烷 nonane 癸烷 decane 十一烷 undecane 十二烷 dodecane Alkane=Number prefix-ane for example:CH4 Methane CH3CH2CH3 Propane CH3CH3 Et

14、hane CH3(CH2)2CH3 Butane CH3(CH2)3CH3 Pentane CH3(CH2)4CH3 Hexane CH3(CH2)5CH3 Heptane CH3(CH2)6CH3 Octane CH3(CH2)7CH3 Nonane CH3(CH2)8CH3 Decane 1119Alkane=Number prefix-decane for example:11-alkane Undecane 12-alkane Dodecane 13-alkane Tridecane 14-alkane Tetradecane 15-alkane Pentadecane 16-alka

15、ne Hexadecane 17-alkane Heptadecane 18-alkane Octadecane 19-alkane Nonadecane 20-alkane Icosane 2129 Alkane=Number prefix-cosane for example:21-alkane Henicosane 22-alkane Docosane 23-alkane Tricosane 24-alkane Tetracosane 25-alkane Pentacosane 30-Alkane Triacontane 3139Alkane=Number prefix-triacont

16、ane for example:31-Alkane Hentriacontane 32-Alkane Dotriacontane 33-Alkane Tritriacontane 34-Alkane Tetratriacontane 35-Alkane pentatriacontane 36-Alkane Hexatriacontane 4090Alkane=Number prefix-contane for example:40 Alkane Tetracontane 50 Alkane Pentacontane 60 Alkane Hexacontane 70 Alkane Heptaco

17、ntane 80 Alkane Octacontane 90 Alkane Nonacontane 100 Alkane Hectane环烃(cyclic hydrocarbons)脂肪环烃(alicyclic hydrocarbons)未取代的饱和单环烃命名时刻在相应的开链烃名前加“环”（cyclo）字。例如：Cyclopropane Cyclohexanecyclobutanecyclopentane Saturated monocyclic hydrocarbons Cyclic alkane=Cyclo-alkane for example:CyclopropaneCyclopenta

18、neCyclohexaneUnsaturated monocyclic hydrocarbons Cyclic alkene=Cyclo-alkene for example:CyclopropeneCyclopentadieneCyclohexen-4-yne1-24Ultraviolet spectrometryUltraviolet spectrometry：Molecular valence electron energy transition.分子价电子能级跃迁分子价电子能级跃迁Wavelength region：160-780 nm.(1)远紫外光区远紫外光区(far UV reg

19、ion):10-200nm (2)近紫外光区近紫外光区(near UV region):200-400nm(3)可见光区可见光区(Vis region):400-780nmElectromagnetic SpectrumEMR encompasses an enormous range of wavelengths and frequencies:Wave properties of electromagnetic radiationEMR is conveniently represented as electric and magnetic fields that undergo in-p

20、hase,sinusoidal oscillations.28SpectroscopyWavelengthWavenumber(cm-1)Quantum Transfer Type-Ray Emission0.005-1.4-Nuclear Spin核自旋X-Ray Absorption 0.1-100-Inner Electron内层电子Vacuum Ultraviolet Absorption10-180 nm1106-5104Bonding Electron价电子UV-VIS Absorption(Emission,Fluorescence)180-780 nm5104-1.3104Bo

21、nding ElectronInfrared Adsorption(Raman Scattering)0.78-300 m1.3104-3.3102Molecule Vibration摆动 (Rotation)Microwave Absorption0.75-3.75 mm13-27Molecule Rotation旋转 Electron Spin Resonance3 cm0.33Electron Spin in Magnetic fieldNuclear Magnet Spin0.6-10 m110-3-1.710-2Nuclear Spin in Magnetic fieldBeers

22、Law (LAMBERT-BEER定律定律)A=-lgT=lg(I0/I)=bcA:absorbance 吸收 T:transmittance透射率Io:intensity of incident beam 入射光强度入射光强度I:intensity of emergent beam 出射光强度出射光强度:molar absorptivity摩尔消光系数b:path length of radiation光程长 c:molar concentration of absorbing analyte浓度Single-Beam or Double-BeamFixed l or DispersiveC

23、ommon:Source Tungsten Halogen Lamp(360-2000 nm)Sample Liquid In CuvetteDispersion Spectrograph w/Diffraction GratingDetector CCDBeers Law:A=ebcAssumptionsApparent Deviations from Beers LawApparent Deviations from Beers LawChromophoreshyperchromic effect/bathochromic shiftL mol-1 cm-1L mol-1 cm-1Auxo

24、phoreUV Absorption of Conjugated Alkenes*lmax175217258e15,00021,00035,000EIncreasing conjugation gives:longer wavelength absorption more intense absorptione units=L mole-1 cm-1b b-Carotene11 double bondslmax =460 nm(e=139,000)lmax(nm)=114+5M+n(48.0-1.7n)16.5Rendo 10Rexon=number of conjugated double

25、bondsM=number of alkyl or alkyl like substituents on the conjugated systemRendo=number of rings with endocyclic double bonds in theconjugated systemRexo=number of rings with exocyclic double bondsFieser-Kuhn RulesUV-Vis spectra of some organic compoundsSaturated hydrocarbons and their derivatives 饱和

26、烃及其取代衍生物饱和烃及其取代衍生物 饱和烃类分子中只含有键，因此只能产生*跃迁，即电子从成键轨道（）跃迁到反键轨道（*）。饱和烃的max一般小于150nm，已超出紫外、可见分光光度计的测量范围，处于真空紫外区。直接用烷烃和卤代烃的紫外吸收光谱分析这些化合物的实用价值不大。但是它们是测定紫外和（或）可见吸收光谱的良好溶剂。Unsaturated hydrocarbon and conjugated alkene 不饱和烃及共轭烯烃(A)Unconjugated alkene 在不饱和烃类分子中，除含有键外，还含有键，它们可以产生*和*两种跃迁。*跃迁的能量小于*跃迁。例如，在乙烯分子中，*跃迁

27、最大吸收波长为180nm左右。C=C 发色基团，但 *200nm。ccHHHH取代基-SR-NR2-OR-Cl CH3 红移距离 45(nm)40(nm)30(nm)5(nm)5(nm)lmax=177nm 助色基团取代 *发生红移177nm 217nm (HOMO LUMO)l lmax （B）conjugated alkene 在不饱和烃类分子中，当有两个以上的双键共轭时，随着共轭系统的延长，*跃迁的吸收带 将明显向长波方向移动，吸收强度也随之增强。共轭双键愈多，红移愈显著，甚至产生颜色。在共轭体系中，*跃迁产生的吸收带又称为K带。K带共轭非封闭体系的*跃迁HOMO:Highest Occ

28、upied Molecular Orbital 最高被占用分子轨道LUMO:Lowest Unoccupied Molecular Orbital分子最低空余轨道l l基基-是由非环或六环共轭是由非环或六环共轭二烯母体二烯母体决定的基准值；决定的基准值；母体基本值：异环二烯异环二烯/无环二烯无环二烯 l l 基基=217 nm 同环二烯同环二烯 l l 基基=253 nm计算共轭烯烃*跃迁最大吸收峰位置的经验规则l lmax=l l基基+nil li 伍德沃德伍德沃德菲泽菲泽 规则规则(Woodwardfieser)nil lI :由双键上取代基种类和个数决定的校正项由双键上取代基种类和个数决

29、定的校正项(1)每延长一个共轭双键每延长一个共轭双键 +30nm(2)环外双键环外双键 +5nm(3)增加一个烷基增加一个烷基（-R）+5 nm（4）增加一个环残基 +5nm（5）酰基（-OCOR）0（6）烷氧基（-OR）+6nm（7）-SR +30nm (8)卤素（-Cl，-Br）+5nm (9)-NR2 +60nm3.Carbonyl compounds 羰基化合物OCRY Y=H,R n *180-190nm aldehydes,ketones,carboxylic acids 羰基化合物含有C=O基团。C=O基团主要可产生*、n*、n*三个吸收带，n*吸收带又称R带带，落于近紫外或紫外

30、光区，R带带吸收较弱（醛、酮、羧酸及羧酸的衍生物，如酯、酰胺等，都含有羰基。由于醛酮这类物质与羧酸及羧酸的衍生物在结构上的差异，因此它们n*吸收带的光区稍有不同。OCRYY=-NH2,-OH,-OR 等助色基团，这些助色团上的n电子与羰基双键的电子产生p共轭共轭,*能量上升，n轨道能量不变K带红移，R 带带兰移移；R带l lmax=205nm；e10-100K K R R n n 177nm Oc n cOccb不饱和醛酮由于产生-共轭K带红移：177250nmR 带红移：290310nm 4.Benzene and its derivatives苯及其衍生物 benzene：带180nm；e

31、=47000带200 nm e=7000 苯环上三个共扼双键的 *跃迁吸收带；230-270 nm e=200 *与苯环振动能级跃迁叠加引起；也称精细结构吸收带(fine structure)。当苯环上有取代基时，苯的三个特征谱带都会发生显著的变化，其中影响较大的是E2带和B谱带，简化，红移。lmax（nm）e max苯200甲苯261300间二甲苯2633001，3，5-三甲苯266305六甲苯272300乙酰苯紫外光谱图羰基双键与苯环共轭：K带强；苯的E2带与K带合并，红移；取代基使B带简化；氧上的孤对电子：R带红移，跃迁禁阻，弱；CC H3On ;R带 ;K带5.立体结构和互变结构对光谱

32、的影响 CCHHCCHH顺反异构顺反异构：顺式：顺式：max=280nm；max=10500反式：反式：max=295.5 nm；max=29000互变异构互变异构：极性溶剂中为极性溶剂中为酮式：酮式：max=204 nm 非非极性溶剂中为极性溶剂中为烯醇式：烯醇式：max=245nm H3CCH2CCOEtOOH3CCHCCOEtOHO6.Effect of solvent on electronic spectra溶剂对吸收光谱的影响COCO非极性 极性 n n n p n pn *跃迁：兰移；兰移；ll；ee *跃迁：红移；ll；ee lmax(正己烷)lmax(氯仿)lmax(甲醇)lmax(水)*230238237243n*329315309305n