第十二章 红外分光光度法.pdf

Chapter?12,?MS?and?IR?1?Chapter?12?Infrared?Spectrophotometry?Chapter?12,?MS?and?IR?2?The?IR?Experiment?Stretching?Vibrations?Atompositions?with?respect?to?each?other?are?not?fixed?!?There?are?relative?movements?to?each?other,?which?can?be?described?by?a?spring-model.?Considering?two?atoms?results?in?the?following?model?Energy-uptake?can?be?accomplished?by?electromagnet?radiation?Stretching?and?Bending?Vibrations?of?three?atoms?a)stretching:?Asymmetrical?stretching?as?Symmetrical?stretching?s?Chapter?12,?MS?and?IR?3?In-plane?bending?(scissoring)?s?Out-of-plane?bending?(wagging)?Out-of-plane?bending?(twisting)?In-plane?bending?(rocking)?Stretching?Frequencies?as?a?function?of?Atomic?Weight:?C-H?3200-2800?cm-1?C-O?1200-1050?cm-1?C-Cl?800-650?cm-1?Chapter?12,?MS?and?IR?4?Stretching?Frequencies?as?a?function?of?Bond?Strengths?Bond?Frequency?(cm-1)?CH2H?2960?(as),?2870?(s)?CCH?3020?CCH?3300?CC?1675-1650?CC?2140-2100?CH2O?1140-1070?CO?1715?Chapter?12,?MS?and?IR?5?Symmetry?is?an?important?factor?of?IR-spectra?since?it?is?associated?with?an?oscillating?electric?dipole.?Ring?strain?The?effect?of?ring?strain?can?be?easily?observed?in?IR:?OOO?Carbonyl-frequency:?1714?cm-1?1746?cm-1?1783?cm-1?C=C?stretching:?1649?cm-1?1656?cm-1?1677?cm-1Chapter?12,?MS?and?IR?6?Stereoisomers:?trans-substituted?alkenes?:?strong?band?at?970?cm-1?cis-substituted?alkenes?:?medium?bands?at?730?cm?1?and?650?cm-1?Conformational?Isomers:?HClOClHOcarbonyl?:?1745?cm-1?1725?cm-1?Chapter?12,?MS?and?IR?7?IR?Spectra?ofAlcohols?CH3CH2OH?CH3CCH3CH3CH2CHCH3CH2OH?A:?O-H?B:?C-H?C:?CH2-vibration?D:?C-O?stretch?Chapter?12,?MS?and?IR?8?IR?Spectra?of?Ketones?CH3COCH3?Chapter?12,?MS?and?IR?9?CH3COCH2CH2CH3?A,?B,?C:?C-H?D:?C=O?E,F,G:?CH2-vibration?IR?Spectra?of?Alkenes?H2CCH(CH2)7CH3?A:?C-H?aliphatic?B:?C-H?olefinic?C:?C=Cstretch?D:?=CH?out?of?plane?and?CH2?Chapter?12,?MS?and?IR?10?IR?Spectra?of?Alkynes?HCCH(CH2)3CH3?A,?C,?E,?due?to?alkyne:?A:?C-H?alkyne?C:?CC?stretch?alkyne?E:?CCH?bend?alkyne?Chapter?12,?MS?and?IR?11?IR?Spectra?of?Aromatic?Compounds?OH?A:?O-H?B:?C-H?C:?Overtones?D:?C=C?aromatic?ring?stretch?CH2OH?Chapter?12,?MS?and?IR?12?CH3CH3?Aromatic?Overtone?and?Combination?Bands?Chapter?12,?MS?and?IR?13?IR?Spectra?of?Amines?N-H?stretch?of?1o?amines:?doublet?at?3500,?3400?cm-1?(very?diagnostic?but?weak?in?intensity)?N-H?stretch?of?2o?amines:?3310-3350?cm-1?(weak)?N-H?bend?of?1o?amines:?1580-1650?cm-1?(medium?to?strong)?N-H?wagging?of?1o?or?2o?amines:?666-909?cm-1?(medium?to?strong,?usually?broad)?CH3(CH2)6CH2NH2?Chapter?12,?MS?and?IR?14?Summary?of?IR?Stretching?Frequencies?Frequency?(cm-1)?Functional?Group?Comments?3300?alcohol?OH?always?broad?amine,?amide?NH?may?be?broad,?sharp,?or?broad?with?spikes?alkyne?CH?always?sharp?3000?alkane?CH?just?below?3000?cm-1?alkene?CH?just?above?3000?cm-1?acid?COOH?very?broad?2200?alkyne?CC?just?below?2200?cm-1?nitrile?NC?just?above?2200?cm-1?1710?(very?strong)?carbonyl?CO?ketones,?aldehydes,?acids,?esters?higher?(1735?cm-1)?amides?lower;?conjugation?(1650?cm-1)?1600-1700?alkene?CC?aromatic?lower;?conjugation?(1600?cm-1)?imine?CN?stronger?than?C=C?amide?CO?stronger?than?C=C?(see?above)?1000-1200?ether?ester?alcohol?CO?Chapter?12,?MS?and?IR?15?