Radical reactions nonchain methods

Unless a substrate or reagent contains an acidic or basic site, the conditions for most radical reactions are neutral. Thus, ionic side reactions such as base-catalyzed epimerization are rarely a problem. While radical reactions are typically conducted at temperatures above ambient, this is often solely for experimental convenience most commercially available initiators require heating to generate radicals. Many radical reactions should succeed at lower temperatures provided that the chain is maintained (in chain methods) or that the rate of generation of radicals is sufficiently rapid (in nonchain methods). Low temperature initiators are available.30,31... 

Although the synthetic transformations that can be accomplished by radical reactions are virtually limitless, precious few general methods exist by which radical reactions can be conducted. These methods can be classified in two main groups chain and nonchain. 

Although chain methods have been the foundation of the recent resurgence of radical reactions in synthesis, many of the earliest preparatively useful radical addition reactions were based on nonchain processes. Of late, such nonchain processes have regained importance. 

A free-radical reaction may proceed by a chain or a nonchain mechanism. There are many experimental methods for determining whether a chain or a nonchain mechanism is operative in a reaction, but these methods don t help much in pen-cil-and-paper problems such as the ones in this book. Luckily, the reagents or reaction conditions will usually indicate which type of mechanism is operative. 

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