各个官能团的位置(含图)

IRSpectroscopyTutorial:AlkanesThespectraofsimplealkanesarecharacterizedbyabsorptionsduetoC–Hstretchingandbending(theC–CstretchingandbendingbandsareeithertooweakoroftoolowafrequencytobedetectedinIRspectroscopy).Insimplealkanes,whichhaveveryfewbands,eachbandinthespectrumcanbeassigned.•C–Hstretchfrom3000–2850cm-1•C–Hbendorscissoringfrom1470-1450cm-1•C–Hrock,methylfrom1370-1350cm-1•C–Hrock,methyl,seenonlyinlongchainalkanes,from725-720cm-1TheIRspectrumofoctaneisshownbelow.Notethestrongbandsinthe3000-2850cm-1regionduetoC-Hstretch.TheC-Hscissoring(1470),methylrock(1383),andlong-chainmethylrock(728)arenotedonthisspectrum.Sincemostorganiccompoundshavethesefeatures,theseC-HvibrationsareusuallynotnotedwheninterpretingaroutineIRspectrum.Theregionfromabout1300-900cm-1iscalledthefingerprintregion.Thebandsinthisregionoriginateininteractingvibrationalmodesresultinginacomplexabsorptionpattern.Usually,thisregionisquitecomplexandoftendifficulttointerpret;however,eachorganiccompoundhasitsownuniqueabsorptionpattern(orfingerprint)inthisregionandthusanIRspectrumbeusedtoidentifyacompoundbymatchingitwithasampleofaknowncompound.IRSpectroscopyTutorial:AlkenesAlkenesarecompoundsthathaveacarbon-carbondoublebond,–C=C–.ThestretchingvibrationoftheC=Cbondusuallygivesrisetoamoderatebandintheregion1680-1640cm-1.Stretchingvibrationsofthe–C=C–Hbondareofhigherfrequency(higherwavenumber)thanthoseofthe–C–C–Hbondinalkanes.ThisisaveryusefultoolforinterpretingIRspectra:OnlyalkenesandaromaticsshowaC-Hstretchslightlyhigherthan3000cm-1.CompoundsthatdonothaveaC=CbondshowC-Hstretchesonlybelow3000cm-1.Thestrongestbandsinthespectraofalkenesarethoseattributedtothecarbon-hydrogenbendingvibrationsofthe=C–Hgroup.Thesebandsareintheregion1000-650cm-1(Note:thisoverlapsthefingerprintregion).Summary:•C=Cstretchfrom1680-1640cm-1•=C–Hstretchfrom3100-3000cm-1•=C–Hbendfrom1000-650cm-1TheIRspectrumof1-octeneisshownbelow.Notethebandgreaterthan3000cm-1forthe=C–Hstretchandtheseveralbandslowerthan3000cm-1for–C–Hstretch(alkanes).TheC=Cstretchbandisat1644cm-1.BandsforC–Hscissoring(1465)andmethylrock(1378)aremarkedonthisspectrum;inroutineIRanalysis,thesebandsarenotspecifictoanalkeneandaregenerallynotnotedbecausetheyarepresentinalmostallorganicmolecules(andtheyareinthefingerprintregion).Thebandsat917cm-1and1044cm-1areattributedto=C&Mac173;Hbends.Itisinterestingtooverlayaspectrumof1-octenewithoctane(shownbelow).Notehowsimilartheyare,exceptforthebandsduetoC=CorC=C–Hstretches/bends.IRSpectroscopyTutorial:AlkynesAlkynesarecompoundsthathaveacarbon-carbontriplebond(–C≡C–).The–C≡C–stretchappearsasaweakbandfrom2260-2100cm-1.Thiscanbeanimportantdiagnostictoolbecauseveryfeworganiccompoundsshowanabsorptioninthisregion.Aterminalalkyne(butnotaninternalalkyne)willshowaC–Hstretchasastrong,narrowbandintherange3330-3270cm-1.(Oftenthisbandisindistinguishablefrombandsresultingfromotherfunctionalgroupsonthesamemoleculewhichabsorbinthisregion,suchastheO-Hstretch.)AterminalalkynewillshowaC–Hbendingvibrationintheregion700-610cm-1.Summary:•–C≡C–stretchfrom2260-2100cm-1•–C≡C–H:C–Hstretchfrom3330-3270cm-1•–C≡C–H:C–Hbendfrom700-610cm-1Thespectrumof1-hexyne,aterminalalkyne,isshownbelow.NotetheC–HstretchoftheC–Hbondadjacenttothecarbon-carbontriplebond(3324),thecarbon-carbontriplebondstretch(2126),andtheC–HbendoftheC-Hbondadjacenttothecarbon-carbontriplebond(636).TheotherbandsnotedareC–Hstretch,scissoring,andmethylrockbandsfromthealkaneportionsofthemolecule.IRSpectroscopyTutorial:AlkylHalidesAlkylhalidesarecompoundsthathaveaC–Xbond,whereXisahalogen:bromine,chlorine,fluorene,oriodine(usuallyBrorClintheorganicchemistryteachinglabs).Ingeneral,C–Xvibrationfrequenciesappearintheregion850-515cm-1,sometimesoutoftherangeoftypicalIRinstrumentation.C–Clstretchesappearfrom850–550cm-1,whileC–Brstretchesappearatslightlylowerwavenumbersfrom690-515cm-1.Interminalalkylhalides,theC–Hwagofthe–CH2Xgroupisseenfrom1300-1150cm-1.Complicatingthespectraisaprofusionofabsorptionsthroughouttheregion1250-770cm-1,especiallyinthesmalleralkylhalides.Notethatallofthesebandsareinthefingerprintregion.Insummary,thefollowingbandsarespecifictoalkylhalides:•C–Hwag(-CH2X)from1300-1150cm-1•C–Xstretches(general)from850-515cm-1oC–Clstretch850-550cm-1oC–Brstretch690-515cm-1Thespectraof1-bromopropaneand1-chloro-2-methylpropaneareshownbelow.NotetheC–BrorC–Clstretchesintheregion850-515cm-1.TheyalsoshowC–BrorC–Clwagintheregion1300-1150cm-1.Eventhoughboth1-bromopropaneand1-chloro-1-methylpropanehavesimilarspectraandthebandsthatdistinguishonefromtheotherareinthefingerprintregion,ifthetwospectraareoverlayed,examinationofthefingerprintregionreadilyshowsthattheyaredifferentcompounds.(Shownbelow.)IRSpectroscopyTutorial:AromaticsThe=C–Hstretchinaromaticsisobservedat3100-3000cm-1.Notethatthisisatslightlyhigherfrequencythanisthe–C–Hstretchinalkanes.ThisisaveryusefultoolforinterpretingIRspectra:OnlyalkenesandaromaticsshowaC–Hstretchslightlyhigherthan3000cm-1.CompoundsthatdonothaveaC=CbondshowC–Hstretchesonlybelow3000cm-1.Aromatichydrocarbonsshowabsorptionsinthere