Chapter10ConjugationinAlkadienesandAllylicSystemsExercisesTheDoubleBondasaSubstituentCVinylicversusAllylicVinylichydrogensareattachedtovinyliccarbonsAllylichydrogensareattachedtoallyliccarbonsVinylicversusAllylicVinylicversusAllylicAllylicCarbocationsThefactthatatertiaryallylichalideundergoessolvolysis(SN1)fasterthanasimpletertiaryalkylhalideThereisgoodevidencefortheconclusionthatallyliccarbocationsaremorestablethanothercarbocationsThereisgoodevidencefortheconclusionthatallyliccarbocationsaremorestablethanothercarbocationsDelocalizationofelectronsinthedoublebondstabilizesthecarbocationResonancemodelOrbitaloverlapmodelResonanceModelOrbitalOverlapModelOrbitalOverlapModelOrbitalOverlapModelOrbitalOverlapModelHydrolysisofanAllylicHalideH2OCH3CH3§10.3ReaonanceRuleRuleRuleRuleRuleRuleCH3OrbitalOverlapModelOrbitalOverlapModelOrbitalOverlapModelOrbitalOverlapModelH2OH2OCH3CH3§10.4AllylicFreeRadicalsAllylicfreeradicalsarestabilizedbyelectrondelocalizationAllylicfreeradicalsarestabilizedbyelectrondelocalizationAllylicfreeradicalsarestabilizedbyelectrondelocalization368kJ/molClCH2CHCH3SelectiveforreplacementofallylichydrogenFreeradicalmechanismAllylicradicalisintermediateC410kJ/molReagentused(insteadofBr2)forallylicbrominationAlloftheallylichydrogensareequivalentAndTheresonanceformsofallylicradicalareequivalentExampleExample§10.6ClassesofDienes(2E,5E)-2,5-heptadiene(2E,4E)-2,4-heptadiene3,4-heptadiene252kJ/mol252kJ/mol126kJ/mol126kJ/molCumulateddoublebondshaverelativelyhighheatsofhydrogenationIsolateddieneIsolateddieneIsolateddieneIsolateddienes-transs-transs-transismorestablethans-cis16kJ/molCumulateddienesarelessstablethanisolatedandconjugateddienesStructureofAlleneAllenesp2BondinginAlleneBondinginAlleneBondinginAlleneAllenesofthetypeshownarechiralAnalogoustodifferencebetween:ascrewwitharight-handthreadandonewithaleft-handthreadaright-handedhelixandaleft-handedhelix590-675℃KHSO4KOHIsolateddienes:doublebondsreactindependentlyofoneanotherCumulateddienes:specializ