生物化学ChapterConjugationinAlkadienesandAllylicSystems.ppt

Chapter 10 Conjugation in Alkadienes and Allylic Systems Exercises 10.1---10.5 10.7---10.13 10.15---10.33 The Double Bond as a Substituent § 10.1 The Allyl Group Vinylic versus Allylic Vinylic versus Allylic Vinylic versus Allylic Vinylic versus Allylic Vinylic versus Allylic Allylic Carbocations §10.2 Allylic Carbocations The fact that a tertiary allylic halide undergoessolvolysis (SN1) faster than a simple tertiary alkyl halide Allylic Carbocations There is good evidence for the conclusion thatallylic carbocations are more stable thanother carbocations Allylic Carbocations There is good evidence for the conclusion thatallylic carbocations are more stable thanother carbocations Stabilization of Allylic Carbocations Delocalization of electrons in the doublebond stabilizes the carbocation Resonance model Orbital overlap model Resonance Model Orbital Overlap Model Orbital Overlap Model Orbital Overlap Model Orbital Overlap Model Hydrolysis of an Allylic Halide Corollary推论Experiment §10.3 Reaonance Introduction to the Rules of Resonance Resonance Model Orbital Overlap Model Orbital Overlap Model Orbital Overlap Model Orbital Overlap Model Hydrolysis of an Allylic Halide Corollary Experiment §10.4 Allylic Free Radicals Allylic free radicals are stabilized byelectron delocalization Allylic free radicals are stabilized byelectron delocalization Spin density is a measure of the unpaired electron distribution in a molecule. shows the unpaired electron in allyl radical divides it time equally between C-1 and C-3. Allylic free radicals are stabilized byelectron delocalization Free-radical stabilities are related tobond-dissociation energies C—H bond is weaker in propene because resulting radical (allyl) is more stable than radical (propyl) from propane Chlorination of Propene Allylic Halogenation Selective for replacement of allylic hydrogen Free radical mechanism Allylic radical is intermediate Hydrogen-atom abstraction step Allylic C—H bo