Chapter 8: Radical Reactivity: Reaction Rate Constants

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Chapter 8 is in a portable document file (pdf) and can be viewed by clicking the blue Chapter 8 button. The drawing below the button illustrates the importance of the reactivity of hydrogen-atom donors to acetoxy group migration. Beside and below this drawing is a summary of Chapter 8.

This drawing shows the product distribution from group migration.
Summary of Chapter 8

Generating a carbon-centered radical represents the beginning point for most radical reactions of carbohydrates. The identity of the radical formed is determined by the rate constant for atom or group transfer from the carbohydrate derivative to a radical that usually is centered on a tin or silicon atom. Compounds that contain iodine or bromine atoms are attractive starting materials for radical reactions because the rate constants for transfer of these atoms to tin- or silicon-centered radicals are quite large. Once a carbon-centered radical has formed, most reactions of importance include a structurally transforming step (e.g., addition of a radical to a compound with a multiple bond or radical cyclization). Rate constants for radical transformation must be large enough that the desired reaction can take place before a competing process, often hydrogen-atom abstraction, intervenes. If a propagation step in a reaction is slower than a chain-terminating reaction, the reaction will undergo chain collapse.