Chapter 8: Addition Reactions of Alkenes

Klein then systematically explores the major addition mechanisms, comparing their rates, regiochemistry, and stereochemical outcomes. The electrophilic addition mechanism is presented as the dominant pathway, where the pi electrons of the alkene act as a nucleophile attacking an electrophile, forming a carbocation intermediate that is subsequently attacked by a nucleophile. The chapter analyzes how carbocation stability determines regioselectivity, with Markovnikov's rule predicting that the electrophile adds to the carbon bearing more alkyl groups, producing the more stable intermediate. Hydration of alkenes, halogenation, hydrohalogenation, and oxymercuration reactions are examined in detail, with explanations of how reaction conditions and reagent choice influence product distribution. The concept of syn versus anti addition is discussed, illustrating how certain mechanisms produce specific stereochemical outcomes. Rearrangement reactions are introduced to explain unexpected products that result from carbocation shift mechanisms. Throughout the chapter, energy diagrams clarify the relative stability of intermediates and transition states, while mechanistic drawings provide visual representations of electron movement. The chapter emphasizes predicting products by analyzing carbocation stability, recognizing when rearrangements occur, and understanding how solvent and temperature affect reaction pathways. This comprehensive treatment of alkene additions provides students with the tools to predict outcomes and explain regioselectivity and stereoselectivity in these crucial transformations.