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1、ChemistryEnglishStateKeyLaboratoryforPhysicalChemistryofSolidSurfaces厦门大学固体表面物理化学国家重点实验室Lecture812.1IntroductionSofarmostofthecompoundswehavestudiedhavebeenopen-chaincompounds.Wealsodiscussedafewringcompounds,thecycloalkanesandcycloalkenes,andfoundtheirpropert
2、iestobeverymuchliketheircounterparts,thealkanesandalkenes.Open-chaincompoundsandtheircorrespondingringcompoundsareknownasaliphatic(脂肪族的）compounds.ThetermaliphaticcomesfromtheGreekwordaleiphar,whichmeans“oil”.Chapter12BenzeneandTheAromaticHydrocarbonsInthischap
3、ter,wewillintroduceanotherclassoforganiccompoundscalledthearomatics（芳香族）.Benzene(苯)anditsderivativeswereoriginallycalledaromaticcompoundsbecauseoftheirratherpleasantaromas.Thetermaromaticnowreferstoanycompoundwhichhasabenzeneringinitsstructureorhaschemicalprop
4、ertiessimilartothoseofbenzene.Inthesectionsthatfollow,wewilldescribethestructureandthepropertiesofbenzeneandmanyofitsderivatives.12.2RingStructureofBenzeneInthe1820s,apureliquidhydrocarboncalledbenzenewasfirstisolated.Chemistsfoundthatthemolecularformulaofthis
5、newsubstancewasC6H6,butittooksometimeforthemtofigureoutastructurewhichwasconsistentwiththepropertiesofbenzene.Open-chainstructures,suchasCH2=CH-C≡C-CH=CH2,werefirstproposed,butitisinconsistentwiththechemicalpropertythatbenzeneundergoessubstitutionwithbromine,i
6、nsteadoftheadditionreactionwithbromine(溴).ThechemistAugustKekulé(1829-1896)proposedanalternativestructureinwhichthesixcarbonatomsofbenzenearejoinedtogethertoformahexagonwitheachringCatombondedtoanHatom.Theinspirationforthisideasupposedlysprangfromadaydreaminwh
7、ichKekulévisualized“longrows…,alltwiningandtwistinginsnakelikemotion,”andthensawthat“Oneofthesnakeshadseizedholdofitsowntail…”.Inanycase,Kekulé‘sstructureturnedouttobecorrect.Benzeneisaringcompound.However,thisstructurealsofailedtoanswermanyquestionsaboutthepr
8、opertiesofbenzene.Ifthestructureabovewerecorrect,benzenewouldstillbeexpectedtobehighlyreactivebecauseofthethreedoublebondsitcontains.Furthermore,ifthebenzeneringreallydidhavealtern
