红外光谱IR课件

-划算--购物推荐群：302284607Charpter3InfraredSpectroscopyVibrationalportionFig.3.1theRelationshipoftheinfraredregiontoothersincludedintheelectromagneticSpectrum红外光Fig.3.2

TheInfraredSpectrumof

polystyrene3.1TheInfraredAbsorptionProcessMoleculesareexcitedtoahigherenergystatewhentheyabsorbIRradiation.8-40kJ/mole,selectivelyRadiationinthisenergyrangecorrespondstotherangeencompassingthestretchingandbendingvibrationalfrequenciesofthebondsinmostcovalentmolecules.Increasetheamplitudeofthevibrationalmotion.OnlythosebondswhichhaveadipolemomentthatchangesasafunctionoftimearecapableofabsorbingIRradiation.Symmetricbonds,suchasthoseofH2orCl2,donotabsorbinfraredradiation.SymmetricorpseudosymmetricAbondmustpresentanelectricaldipolewhichischangingatthesamefrequencyastheincomingradiationinorderforenergytobetransferred.Thechangingelectricaldipoleofthebondcanthencouplewiththesinusoidallychangingelectromagneticfieldoftheincomingradiation.Asymmetricbondwhichhasidenticalornearlyidenticalgroupsoneachendwillnotabsorbintheinfrared.theModesofStretchingandBendingSymmetricStretchAsymmetricStretchInplaneRockingScissoringOutofplaneWaggingTwistingSymmetricStretchAsymmetricStretch~2872cm-1~2962cm-1Methyl~1760cm-1~1800cm-1Anhydride~3300cm-1~3400cm-1Amino~1350cm-1~1550cm-1NitroComplicatedSpectrum?Fundamentalabsorptions:thegroundstatetothelowest-energystate.

Overtones:2,3,…

Combinationbands:

Differencebands:

Fermiresonance:afundamentalvibrationcoupleswithanovertoneorcombinationband.Carbonylcompounds

Rotationalcouplingmayleadtoaconsiderableamountofunresolvedfinestructure.StrongerbondshavealargerforceconstantKandvibrateathigherfrequenciesthanweakerbonds.

C-C C=C C≡C

1200cm-11650cm-1 2150cm-1

increasingK

Astheatombondedtocarbonincreasesinmass,thereducedmass()increases,andthefrequencyofvibrationdecreases.C－HC－CC－OC－ClC－BrC－I3000cm-11200cm-1

1100cm-1750cm-1600cm-1500cm-1 increasingμBendingmotionsoccuratlowerenergy(lowerv)thanthetypicalstretchingmotionsbecauseofthelowervalueforK.

C－Hstretching C－Hbending

~3000cm-1

~1340cm-1

HybridizationaffectstheforceconstantK，sp>sp2>sp3

sp sp2 sp3

≡C－H=C－H －C－H3300cm-1 3100cm-1 2900cm-1

ResonancehastheeffectofreducingtheforceconstantK,andtheabsorptionmovestoalowerfrequency.C=O(normal)C=O(conjugated)1715cm-1 1675~

1680cm-13.5theInfraredSpectrometerFT-IR(FourierTransformInfraredSpectrometer)GreaterspeedGreatersensitivityBettersignal-tonoiseFig.3.4AschematicdiagramofaFT-IRSpectrometerMichelsonInterferometerSolids:KBrpelletThemaindisadvantageofthismethodisthatKBrabsorbwater.Nujolmullmethod:grindthecompoundwithmineraloil(Nujol)tocreateasuspensionofthefinelygroundsampledispersedinthemineraloil.Nujolbandsappearat2924,1462,and1377cm-1.Fig.3.6Gas

Fig.3.7theGasCell3.7WhattoLookforWhenExaminingInfraredSpectraFig.3.8Theinfraredspectrumof3-methyl-2-butanone(neatliguid,KBrplates).

Characteristictheposition(wavenumbers)theintensitytheshapeC=O

at1715cm-1strongabsorptionbroadpeak12Fig.3.10AComparisonoftheShapesoftheAbsorptionBandsfortheO-HandN-HGroupsO-H 3650-3200cm-1

N-H 3500-3300cm-13.8CorrelationChartsandTablesTable3.2ASimplifiedCorrelationChartFig.3.11Absorptionbandsofbonds3.9HowtoApproachtheAnalysisofaSpectrum(orwhatyoucantellataglance)TheC=O,O-H,N-H,C-O,C=C,C≡C,C≡N,andNO2peaksarethemostconspicuousandgiveimmediatestructuralinformationiftheyarepresent.DonottrytomakeadetailedanalysisoftheC-Habsorptionsnear3000cm-1;almostallcompoundshavetheseabsorptions.Theimportantgrossfeatures1.Isacarbonylgrouppresent?1820-1660cm-1,oftenthestrongestabsorptionandofmediumwidth.IfC=Oispresent:Broadabsorptionnear3400-2400cm-1→O-H→acidsMediumabsorptionnear3400cm-1(oradoublepeak)→N-H→amidesStrong-intensityabsorptionsnear1300-1000cm-1→C-O→estersTwoC=Oabsorptionsnear1810and1760

cm-1→anhydridesTwoweakabsorptionsnear2850and2750

cm-1→aldehydesTheprecedingfivechoiceshavebeen

eliminated→ketonesIfC=Oisabsent:Broadabsorptionnear3400-3300cm-1→O-H,confirmthisbyfindingC-Onear1300-1000cm-1→alcohols,phenolsMediumabsorption(s)near3400cm-1→N-H→aminesCheckfor

C-Onear1300-1000cm-1(andabsenceofO-Hnear3400cm-1→ethersC-H bendingCH2 1465cm-1(m)CH3 1450cm-1,1375cm-1(m)Along-chainband(CH2)nbending(rocking),n≥4,720cm-1C-Cstretchnotinterpretativelyuseful;manyweakpeaks Fig.3.12theInfraredSpectrumofDecane（癸烷）

Fig.3.13theInfraredSpectrumofmineraloil

Fig.3.14theInfraredSpectrumofCyclohexaneB.Alkenes=C-H stretch(sp2) >3000cm-1(m)(3095-3010cm-1) out-of-plane(oop)bending 1000-650cm-1(s)C=C stretch 1660-1600cm-1(m-w)conjugationmovesC=Cstretchtothelowerfrequenciesincreasestheintensitysubstitutedsymmetricallysubstitutedbondsnoabsorptionsymmetricallydisubstituteddoublebonds

trans

vanishinglyweakcis

strongerFig.3.15theInfraredSpectrumof1-HexeneFig.3.16theInfraredSpectrumofCyclohexeneFig.3.17theInfraredSpectrumofcis-2-PenteneFig.3.18theInfraredSpectrumoftrans-2-Pentene≡C-H(sp)

stretch

near3300cm-1(s)C≡C stretch

near2150cm-1(m-w)C.Alkynesconjugationmovestolowerfrequency.disubstitutedorsymmetricallysubstituted

noabsorptionorweakabsorptionFig.3.20theInfraredSpectrumof4-octyneFig.3.19theInfraredSpectrumof1-octyneStrainmovesabsorptiontoleftIncreasingscharactermovesabsorptiontoleftFig.2.21theC-HStretchRegionC-HStretchRegion 3300-2750cm-1Table3.4StretchingVibrationsforVarioussp3-HybridizedC-HBondsFig.3.22theC-HBendingVibrationsforMethylandMethyleneGroupsC-HBendingVibrationsforMethylandMethyleneFig.3.23C-HBendingPatternsfortheIsopropylandt-butylGroupsC=CStretchingVibrationsSimpleAlkyl-SubstitutedAlkenes1670-1640cm-1TheC=Cfrequenciesincreaseasalkylgroupsareaddedtoadoublebond.

mono-1640cm-1,di-1650cm-1,tri-andtetra-1670cm-1

trans-Disubstitutedalkenesabsorbathigherfrequencies(1670cm-1)thancis-disubstitutedalkenes(1658cm-1).Ratherweakintensity,inmanycases(tetrasubstituted),notobservedcis-Alkenes(lesssymmetry)absorbmorestronglythantrans-alkenesDoublebondsinringsabsorbmoreweaklythanthosenotcontainedinrings.Terminaldoublebondsinmonosubstitutedalkenesgenerallyhavestrongerabsorption.ConjugationEffectsConjugationmovesthepeaktotheright.vinyldoubleinstyrene1630cm-1ConjugatedwiththeC=O,theC=Cabsorptionshiftstolowerfrequency,andisintensifiedbythestrongdipoleoftheC=O.Endodoublebonds1650cm-11646161115661656Ring-SizeEffectswithInternalDoubleBondsFig.3.24C=Cstretchingvibrationsinendocyclicsystems

~

1611cm-1nocoupleC-Csingle-bondstretchingvibrationcanberesolvedintotwocomponents(aandb).ComponentaisinlinewiththeC=Cstretchingvector,theC-CandC=Cbondsarecoupled,leadingtoahigherfrequencyofabsorption.1656cm-11788cm-11883cm-11566cm-11641cm-11675cm-11611cm-11650cm-11679cm-11646cm-11675cm-11681cm-1Fig.3.25TheeffectofalkylsubstitutiononthefrequencyofaC=Cbondinaring1940cm-11780 1678 1657 1655 1651ExodoublebondsRing-SizeEffectswithExternalDoubleBondsFig.3.26C=Cstretchingvibrationsinexocyclicsystems.C-HBendingVibrationsforAlkenesin-plane(scissoring)forterminalalkenes

1415cm-1(m-w)out-of-plane

1000-650cm-1(s)Fig.3.27TheC－HOut-of-planeBendingVibrationsforSubstitutedAlkenesC=C1670cm-1VeryweakOvertone1820,vinylMonosubstituteddoublebondsTwostrongbandsforalkyl-substituted,990,910

Releaseelectronsgroups(Cl,F,OR)shiftthe910bandtoright,810Withdrawelectronsgroups(C=O,C≡C)shiftthebandtoleft,9601,2-Disubstituteddoublebondscis-,700,andtrans-,970

1,1-disubstituteddoublebonds,890Trisubstituteddoublebonds,815Tetra-,noabsorption=C-H stretch(sp2) >3000cm-1=C-H oop 900-690cm-1C=C ringstretch 1600cm-1,1475cm-1Overtone/combinationbands 2000-1667cm-13.11AromaticringsFig.3.28theInfratedSpectrumofToluenebackFig.3.29theInfraredSpectrumofortho-DiethylbenzeneFig.3.30theInfraredSpectrumofmeta-DiethylbenzeneFig.3.31theInfraredSpectrumofpara-DiethylbenzeneFig.3.32theInfraredSpectrumofStyrenebackIn-plane,1300-1000cm-1,rarelyuseful.Out-of-plane,900-690cm-1,farmoreuseful,extremelyintense,resultingfromstrongcouplingwithadjacentH,canbeusetoassignthepositionofsubstituentsonthearomaticring.oopbendingvibrationsismostreliableforalkyl-,alkoxy-,halo-,amino-,orcarbonyl-substitutedaromaticcompounds.Aromaticnitrocompounds,derivativesofaromaticcarboxylicacids,andderivativesofsulfonicacidsoftenleadtounsatisfactoryinterpretation.C-HBendingVibrationsDiscussionReliableinterpretationUnreliableinterpretationFig.3.33C-Hout-of-planeBendingVibrationsforSubstitutedBenzenoidCompoundsSubstitutedRings690cm-1,strong;ifabsent,nomono-；Beobscuredbythehalocarbon

solvents(strongC-X)750cm-1,strong750690780880800-850720-667cm-1fromC=CoopringbendingCombinationsandOvertoneBandsWeak,thesebandsarebestobservedbyusingneatliquidsorconcentratedsolutions.Ifthecompoundhasahigh-frequencycarbonylgroup,thisabsorptionwilloverlaptheweakovertonebandssothatnousefulinformationcanbeobtainedfromtheanalysisoftheregion.ConsistentwiththeoopbendingvibrationsFig.3.34the2000-to-1667RegionforSubstitutedBenzenoidCompoundsback3.12AlcoholsandPhenolsO-H stretchfree 3650-3600cm-1,sharppeakH-bonded 3400-3300cm-1,broadpeakC-O-Hbend1440-1220cm-1,abroadandweakpeakC-O stretch 1260-1000cm-1O-Hin-planebendingabsorptionnear1360cm-1,usuallyoverlapstheC-Hbendingvibration(CH3,1375cm-1).Fig.3.35TheInfraredSpectrumof1-HexanolFig.3.36TheInfraredSpectrumof2-ButanolFig.3.37TheInfraredSpectrumofpara-CresolO-HStretchingVibrationsFig.3.38theO-HStretchRegiondilutesolutionDiscussionverydilutesolutionpure(neat)liquidfilm,intermolecularH-bondingIntramolecularH-bondingMethylsalicylate

3200cm-1Normalphenols3350cm-1

Presentinortho-carbonyl-substitutedphenols,usuallyshiftsthebroadO-Hbandtoright. TheintramolecularH-bondedbanddoesnotchangeitspositionsignificantlyevenathighdilution.C-O-HBendingVibrationscoupledtoH-C-Hbending

1440-1220cm-1,someweakandbroadpeaks,oftenobscuredbyCH3bendings.C-OStretchingVibrationsStrongabsorptionbands1260-1000cm-1TheC-OabsorptionsarecoupledwiththeadjacentC-C

stretchingvibrations,thepositionofthebandmaybeusedtoassignaprimary,secondary,ortertiarystructuretoanalcoholortodeterminewhetheraphenoliccompoundispresent.OconjugateswiththeringshiftstheC-Obandtoleft(moredouble-bondcharacter)1220cm-1phenolsDecreaseIncreaseTable3.5C-OandO-HStretchingVibrationsinAlcoholsandPhenolsTheseC-OabsorptionsareshiftedtolowerfrequencieswhenunsaturationispresentonadjacentCorwhentheO-Hisattachedtoaring.Shiftsof30-40cm-1fromthebasevaluesarecommon.Fig.3.39theInfraredSpectrumofPropargyl3.13Ethers

C-Ostretchthemostprominentband1300-1000cm-1AbsenceofC=OandO-HisrequiredtoensurethatC-Ostretchisnotduetoanesteroranalcohol.Phenylalkylethersgivetostrongbandsatabout1250and1040cm-1.Aliphaticethersgiveonestrongbandatabout1120cm-1.Fig.3.40TheInfraredSpectrumofDibutylEtherFig.3.41TheInfraredSpectrumofAnisole（茴香醚）C-O-Cstretch 1300-1000cm-1,VinylethersAlcoholsandestersalsogivestrongbandDiscussion

1120cm-1 strong asymmetricC-O-Cstretching

850cm-1 veryweak

symmetricstretchingbandasix-memberedringcontainingoxygen,1120cm-1,Dialkylethers,Aryletherstwostrongbands1250cm-1

1040cm-1

1220cm-1

strong

asymmetricC-O-Cstretch

850cm-1

veryweak

symmetricstretchThroughresonance,theC-Obandshiftedtoleftbecauseoftheincreaseddouble-bondcharacter,whichstrengthensthebond.ResonanceincreasesthepolarcharacteroftheC=Cdoublebond,thebandat1640cm-1isconsiderablystrongerthaninnormalC=Cabsorption.Resonance1220cm-1Noresonance1120cm-1,EpoxidesSmallringcompoundsusuallygivethreebands:

1280-1230cm-1,weakring-stretchingband

950-815cm-1,strongring-deformationbandsasymmetric

880-750cm-1,strongsymmetricmono-,835cm-1;

di-,

775cm-1,AcetalsandKetals1200-1020cm-1,fourorfivestrongbands

thesebandareoftenunresolved3.14CarbonylCompoundsaldehydes,ketones,acids,esters,amides,acidchlorides,andanhydrides1850-1650cm-1,strongabsorptionC=OstretchingfrequencyissensitivetoattachedatomsC=Ofrequencyofaketone,isusuallyconsideredthereferencepointcm-1181018001760173517251715

17101690AnhydrideAcidAnhydrideEsterAldehydeKetoneCarboxylicAmide(band1)chloride(band2)acidFig.3.42normalbasevaluesfortheC=OstretchingvibrationsforcarbonygroupsElectron-withdrawingeffects(inductiveeffects)ResonanceeffectsHydrogenbondingInacidchlorides,thehighlyelectronegativehalogenatomstrengthenstheC=Obondthroughanenhancedinductiveeffectandshiftsthefrequencytoevenhighervaluesthanarefoundinesters.Resonanceeffect(NconjugatewithC=O)lowersC=OfrequencyExplanationElectron-withdrawingeffectraisesC=OfrequencyEsterAmideAnhydrides~1760cm-1Symmetric

~1800cm-1AsymmetricCarboxylicacidShifttohigherfrequenciesbecauseofaconcentrationofelectronegativeOTwobandsinmonomericforminverydilutesolution,1760cm-1inconcentratedsolution,intheformofneatliquid,orinthesolidstate(KBrpelletandNujol)tendtodimerizeviaH-bonding,weakenstheC=O,lowerstheforceconstantK,resultinginaloweringofC=Ofrequencyofsaturatedacids,1710cm-1Ketonesabsorbatalowerfrequencythanaldehydesbecauseoftheiradditionalalkylgroup,whichiselectron-donating(comparedtoH)andsupplieselectronstotheC=Obond.Thiselectron-releasingeffectweakenstheC=Obondintheketoneandlowerstheforceconstantandtheabsorptionfrequency.1715cm-11725cm-1verseA.FactorswhichinfluencetheC=OstretchingvibrationDelocalizationofthe

electronsintheC=C

andC=Obonds.Conjugationincreasesthesingle-bondcharacteroftheC=O

andC=CbondsintheresonancehybridandhencelowersK,shiftsthebandstoright.,

doublebondresultsin25-45cm-1

loweringoftheC=Ofrequency.Additionofunsaturation(,)resultsinafurthershifttolowerfrequency,butonlybyabout15cm-1

more.TheC=Cshiftsfrom1650to1640cm-1,andtheabsorptionisgreatlyintensified.ConjugationEffectsRotationalIsomersOftentwocloselyspacedC=Oabsorptionpeaksareobservedfortheseconjugatedsystems,resultingfromtwopossibleconformations,thes-cisands-trans.Thes-cisconformationabsorbsatahigherfrequencythanthes-transconformation.Insomecases,theC=Oabsorptionisbroadenedratherthansplitintothedoublet.s-ciss-trans,

-unsaturatedketone1715→1690cm-1Aryl-substitutedacid1710→1680cm-1ConjugationdoesnotreducetheC=Ofrequencyinamides.Theintroductionofsp2hybridizedCremoveselectrondensityfromtheC=Oandstrengthensthebondinsteadofinteractingbyresonanceasinothercarbonylexamples.Sincetheparentamidegroupisalreadyhighlystabilized,theintroductionoftheC=Cdoesnotovercomethisresonance.Aryl-substitutedaldehye1725→1700

RingSizeEffectsSix-memberedringswithC=Oareunstrained,1715cm-1DecreasingtheringsizeincreasesthefrequencyoftheC=OAllofthefunctionalgroupslistedinFig.3.45,whichcanformrings,giveincreasedfrequenciesofabsorptionwithincreasedanglestrain.Forketonesandesters,thereisoftena30cm-1increaseinfrequencyforeachCremovedfromtheunstrainedsix-memberedringvalues.Cyclicketone1715→1745cm-1Cyclicketone1715→1780cm-1Cyclicester(lactose)1735→1770cm-1Cyclicamide(lactam)1690→1705cm-1Inketones,largerringshavefrequencieswhichrangefromnearlythesamevalueasincyclohexanonetovaluesslightlylessthan1715cm-1.eg.Cycloheptanone,1705cm-1.WhentheCnexttotheC=Oissubstitutedwithachlorine(orotherhalogen)atom,theC=Obandshiftstoahigherfrequency.Theelectron-withdrawingeffectremoveselectronsfromtheCoftheC=Obond.Thisremovaliscompensatedforbyatighteningofthebond(shortening),whichincreasestheforceconstantandleadstoanincreaseintheabsorptionfrequency.-SubstitutionEffectsEquatorialchlorine~1750cm-1WhentheClisnexttoC=O,nonbondedelectronsontheOarerepelled,resultinginastrongerbondandahigherabsorptionfrequency.Axialchlorine~1725cm-1Hydrogen-BondingEffetsHbondingtoC=OlengthenstheC=ObondandlowersthestretchingforceconstantK,resultinginaloweringoftheabsorptionfrequency.1680cm-11710cm-1KetoneTautomerof,

-Diketone~1720cm-1(doublet)EnolTautomerof,

-Diketone~1640cm-1B.AldehydesC=O stretch 1740-1725cm-1(vertstrong) C-H stretch 2750cm-1,2850cm-1(w),doublet

Ifthe2750cm-1bandispresenttogetherwiththeproperC=Oabsorptionvalue,analdehydefunctionalgroupisalmostcertainlyindicated.

Fig.3.43TheInfraredSpectrumofNonanal（壬醛）

CH2oftenabsorbmorestronglywhenCH2areattacheddirectlytoC=OFig.3.44TheInfraredSpectrumofCrotonaldehyde（巴豆醛）Fig.3.45TheInfraredSpectrumofbenzaldehyde（安息香醛）C.KetonesC=O stretch 1720-1708cm-1

bend1300-1100cm-1(m)Fig.3.46TheInfraredSpectrumofMesitylOxide(异亚丙基丙酮)

back1700-16751644-1617Fig.3.47TheInfraredSpectrumofAcetophenone

ConjugationoftheC=Owithphenyl;1700-1680cm-1forC=Oand1600-1450cm-1forring.Conjugationwithtwoaromaticrings;1670-1600cm-1forC=O.ConjugationFig.3.48TheC=OStretchingVibrationsforConjugatedKetones1715171516951685168016651640cm-1Normal,-unsaturatedEnolic-Diketones

Fig.3.49TheInfraredSpectrumofCyclopentanoneCyclicKetones(RingStrain)C=Ofrequencyincreaseswithdecreasingringsize.ThescharacterintheC=Ogroupincreasesastheringsizedecreases,untilitreachesamaximumvaluethatisfoundinthesp-hybridizedC=Oinketene.RingStrain2140181517801745171517151705cm-1Normal=C=OKeteneFig.3.50TheC=OStretchingVibrationsforCyclicKetonesandKetene-Diketones(1,2-Diketones)1716cm-1,onestrongabsorptionpeak1680cm-1,anarrowlyspaceddoublet-Diketones(1,3-Diketones)KetotautomerC=Odoublet1723cm-1(symmetricstretch)1706cm-1(asymmetricstretch)EnoltautomerC=O(H-bonded),1622cm-1O-H(H-bonded),3200-2400cm-1InternalH-bonding&ResonanceshifttheC=Obandto1622cm-1.O-Hstretch,weak,broad,3200-2400cm-1.TherelativeintensitiesoftheenolandketoC=Oabsortionsdependonthepercentagespresentatequilibrium.H-bondedC=Oinenolforms:1640-1670cm-1,theketoforms(doublets):1730-1695cm-1.Fig.3.51TheInfraredSpectrumof2,4-Pentanedione-HaloketonesSubstitutionofahalogenatomonthe

CshiftstheC=Opeaktoahigherfrequency.Similarshiftsoccurwithotherelectron-withdrawinggroups,suchasanalkoxygroup(-O-CH3).Whenthemoreelectronegativefluorineatomisattached,thefrequencyshiftstoanevenhighervalue.1750cm-11731cm-11781cm-1Amedium-intensitybandforCH3adjacenttoC=Oatabout1370cm-1forthesymmetricbendingvibration.TheseCH3absorbwithgreaterintensitythanCH3foundinhydrocarbons.C-CO-C 1300-1100cm-1(m-s)coupledstretchingandbendingAliphaticketones1220-1100cm-1

Aromaticketones

1300-1220cm-1BendingModesD.CarboxylicAcidsO-H stretch3400-2400cm-1,

verybroad,overlapsC-HC=Ostretch 1730-1700cm-1,verystrong,broadC-O stretch 1320-1210cm-1,mO-H(H-bonded)oop930cm-1,w-m,broadFig.3.52TheInfraredSpectrumofIsobutyricAcidFig.3.53TheInfraredSpectrumofBenzoicAcidIftheextremelybroadH-bondedbandispresenttogetherwiththeproperC=Oabsorptionvalue,acarboxylicacidisalmostcertainlyindicated.C=Obandisusuallybroaderandmoreintensethanthatpresentinanaldehydeoraketone.Formostacidsinverydilutesolution,1760-1730cm-1forthemonomer.E.EstersC=O stretch 1750-1735cm-1ConjugationinRpartmovesthebandright,15-25cm-1;ConjugationwiththeOintheR’partmovesthebandleft,25cm-1;Ringstrainincyclicesters(lactones)movesthebandleft.C-O stretch 1300-1000cm-1

Stretchintwoormorebands,onestrongerandbroaderthantheother.1738cm-11725cm-11724cm-11762cm-11765cm-1Fig.3.54TheInfraredSpectrumofEthylButyrate

ThestrongandbroadC-OstretchingbandsaredifferentfromtheweakerandnarrowbandsofketonesFig.3.56TheInfraredSpectrumofMethylBenzoateFig.3.55TheInfraredSpectrumofMethylMethacrylateConjugationwiththeestersingle-bondedOFig.3.57TheInfraredSpectrumofVinylacetate1762cm-1IntensityisincreasedHydrogen-BondingEffectsFig.3.58TheInfraredSpectrumofMethylSalicylate1680cm-1CyclicEsters(Lactones)TheC=Ovibrationsareshiftedtohigherfrequencieswithdecreasingringsize.Table3.6EffectsofRingSize,,Unsaturation,andConjugationwithOxygenontheC=OVibrationsinLactonesFig.3.59TheInfraredSpectrumofγ-Butyrolactone-HaloEstersHalogenationontheCleadstoanincreaseintheC=Ofrequency.-KetoEstersUsuallyashoulderonthemainabsorptionbandnear1735cm-1orasinglebroadenedabsorptionband.

-KetoEsters(tautomerization-KetoEsters)

strongdoublet,1720cm-1,1740cm-1.“enol”tautomer,weakdoublet,1650cm-1.C-O

StretchingVibrationinEsters 1300-1150cm-1，ThestrongestandbroadestbandEstersofaromaticacidsnearerthehigher-frequencyend.Estersofsaturatedacidsnearerthelower-frequencyend.1150-1000cm-1,Aweakerband

EstersAtleastoneverystrongandbroadabsorptioninthisrange1300-1000cm-1.F.AmidesC=O Stretch 1680-1630cm-1N-H stretch 3475-3150cm-1

primaryamides(2bands) 3350cm-1,as,3180cm-1,ssecondaryamides(1band) 3300cm-1N-H bending 1640-1550cm-1P-andS-,insolidphase,broadC=Oband,1680-1630cm-1,overlapstheN-Hbendingband(1640-1620cm-1),makingtheC=Obandappearasadoublet.Inverydilutesolution,thebandappearsatabout1690cm-1.Cyclicamides(lactams)givetheexpectedincreaseinC=Ofrequencyfordecreasingringsize.1660cm-11705cm-11745cm-1Fig.3.61TheInfraredSpectrumofN-MethylacetamideFig.3.60TheInfraredSpectrumofPropionamideC-NStretchingBands C-Nstretchingband,1400cm-1forP-amides.N-H

BendingBandsP-,inthesolidphase,strongbendingbands1640-1620cm-1;otherbendingbandsatabout1125cm-1andaverybroadband750-600cm-1.S-,relativelystrongbendingbandsatabout1550cm-1,(acombinationofaC-NstretchingbandandaN-Hbendingband.G.AcidChloridesC=O stretch 1810-1775cm-1

conjugationlowersthebandto1780-1760cm-1C-Cl stretch 730-550cm-1Fig.3.62TheInfraredSpectrumofAcetylChloride（乙酰氯）overtoneFig.3.63TheInfraredSpectrumofBenzoylChloride1774cm-1H.AnhydridesC=O stretch（as） 1830-1800cm-1 stretch（s） 1775-1740cm-1C-O stretch 1300-900cm-1,multiplebands

strongandbroadFig.3.64TheInfraredSpectrumofPropionicAnhydride3.15AminesN-H stretch(N-H) 3500-3300cm-1

P- 2bands(as,s);3400and3300cm-1 S- 1band;3300cm-1;oftenvanishinglyweak aromaticS-,strongernear3400cm-1 T-

nobandN-H bend(N-H) P-,1640-1560cm-1,(m-s,broad) S-,1500cm-1aromatic;aliphatic,veryweak

N-H OOP,broad near800cm-1

(aliphaticamines)C-N stretch 1350-1000cm-1,m-s

aliphatic,1250-1000cm-1,aromatic,1350-1250