章链二烯丙基体系共轭拉丁动词意为columbia有机化学课件04 html1.pptx

Chapter10

ConjugationinAlkadienesand

AllylicSystemsconjugareisaLatinverbmeaningto

linkoryoketogether

allyliccarbocationTheDoubleBondasaSubstituentC+CC

allyliccarbocationallylicradicalTheDoubleBondasaSubstituentC+CC?CCC

allyliccarbocationallylicradicalconjugateddieneTheDoubleBondasaSubstituentC+CC?CCCCCCC

CCCHHHHH10.1

TheAllylGroup

vinyliccarbonsallyliccarbonVinylicversusAllylicCCC

vinylichydrogensareattachedtovinyliccarbonsVinylicversusAllylicCCCHHH

allylichydrogensareattachedtoallyliccarbonsVinylicversusAllylicCCCHHH

VinylicversusAllylicCCCXXXvinylicsubstituentsareattachedtovinyliccarbons

VinylicversusAllylicCCCXXXallylicsubstituentsareattachedtoallyliccarbons

10.2

AllylicCarbocationsCCC+

thefactthatatertiaryallylichalideundergoes

solvolysis(SN1)fasterthanasimpletertiary

alkylhalideClCH3CH3CH3relativerates:(ethanolysis,45°C)1231AllylicCarbocationsCClCH3CH3CH2CCH

providesgoodevidencefortheconclusionthat

allyliccarbocationsaremorestablethan

othercarbocationsCH3CH3CH3formedfasterAllylicCarbocationsCCH2CCH++CH3CH3

providesgoodevidencefortheconclusionthat

allyliccarbocationsaremorestablethan

othercarbocationsCH3H2C=CH—stabilizesC+betterthanCH3—AllylicCarbocationsCCCH3CH3H2CCH++CH3CH3

Delocalizationofelectronsinthedouble

bondstabilizesthecarbocation resonancemodel

orbitaloverlapmodelStabilizationofAllylicCarbocations

ResonanceModelCH3CH3H2CCH+CCH3CH3H2CCH+C

ResonanceModelCH3CH3H2CCH+CCH3CH3H2CCH+CCH3CH3H2CCHd+Cd+

OrbitalOverlapModeld+d+

OrbitalOverlapModel

OrbitalOverlapModel

OrbitalOverlapModel

H2ONa2CO3(85%)(15%)HydrolysisofanAllylicHalideClCH3CH3CH2CCHOHCH3CH3CH2CCH+CH3HOCH2CHCCH3

H2ONa2CO3(85%)(15%)CorollaryExperimentOHCH3CH3CH2CCH+CH3HOCH2CHCCH3CH3ClCH2CHCCH3

CH3ClCH2CHCCH3ClCH3CH3CH2CCHandgivethesameproductsbecausethey

formthesamecarbocation

CH3ClCH2CHCCH3ClCH3CH3CH2CCHandgivethesameproductsbecaus