Chapter 6: Radical Reactions in Organic Synthesis

The discussion progresses to chain propagation mechanisms that sustain radical transformations, with particular attention to how radical stability and structural features govern reactivity and selectivity outcomes. Students learn how radical reactions achieve regioselective and stereoselective bond formation through mechanistic understanding and judicious choice of reaction conditions. The chapter details significant synthetic applications including the selective halogenation of alkane substrates, intramolecular cyclization processes that construct ring systems, and atom transfer mechanisms that enable carbon-carbon and carbon-heteroatom bond construction. Named reactions such as the Barton transformation and Hunsdiecker process are analyzed mechanistically to illustrate how radical intermediates accomplish synthetically valuable rearrangements and functional group interconversions. A major emphasis concerns the practical control of radical reactivity through initiator selection, the incorporation of inhibitory reagents that suppress unwanted side reactions, and the strategic use of mediating agents such as tin hydrides and nitroxyl radical species that fine-tune reaction pathways. Through detailed mechanistic examples and synthetic case studies, the chapter demonstrates how radical chemistry solves otherwise intractable synthetic problems, particularly in constructing strained ring systems and challenging polycyclic architectures that conventional ionic methods cannot access, establishing radical reactions as an indispensable modern synthetic strategy.