CHE-2201 Lecture Notes - Lecture 11: Bond-Dissociation Energy, Regioselectivity, Halogenation
Document Summary
Free radicals form when bonds break homolytically. I. e. , the single-barb or fishhook arrow that shows movement. Free radicals can be thought of as sp2 hybridized or quickly interconverting sp3 hybridized. From least to most stable free radicals: If the free radical is more stable, it is easier to take the h off. Bond dissociation energy (bde) decreases as you move from methyl to tertiary free radicals. Allylic and benzylic are easier to generate a radical. Unlike a carbocation, a radical will not rearrange to produce a more stable radical. Termination: removal of a radical (usually via two radicals combining) Chain reactions: the products from one step are reactants for a different step in the mechanism. An initiator starts a free radical chain reactions. Chlorination is more product favored than bromination. New chirality center is formed with halogenation of butane or more complex alkanes. When a c=c is present it affects the regioselectivity of the halogenation reaction.
