Chapter 10: Reactions of Alkenes

Students learn how carbocation intermediates form and rearrange to more stable configurations, with particular emphasis on understanding stability hierarchies among primary, secondary, tertiary, allylic, and benzylic carbocations through hyperconjugation effects. The chapter then covers practical hydration methods including oxymercuration-demercuration sequences and hydroboration-oxidation reactions, both of which showcase important stereochemical outcomes such as syn and anti addition patterns that control product stereochemistry. Additional transformations explored include dihydroxylation using osmium tetroxide, halogenation with bromine and chlorine that proceed through halonium ion intermediates, and epoxidation via peroxy acid mechanisms that produce three-membered ring oxides. The chapter details oxidative cleavage strategies, particularly ozonolysis and permanganate oxidation, which fragment the alkene to yield aldehydes, ketones, or carboxylic acids depending on substitution patterns and conditions. Cyclopropane synthesis receives attention through both dichlorocarbene addition and the Simmons-Smith reaction using organozinc reagents, demonstrating alternative approaches to ring formation. The chapter concludes with catalytic hydrogenation across palladium or platinum catalysts as a straightforward method for alkene saturation. Throughout, detailed reaction mechanisms and strategic considerations equip students to predict products and understand the factors governing selectivity in alkene chemistry.