Ground- and Excited-State Carboxylate Radical Chain Carriers. Radical Chain Substitution Reactions with Acyl Hypohalites

Article abstract of DOI:10.1021/ja00350a043

Earlier work with aliphatic carboxylate radicals held no prospect that they could be used as hydrogen abstractors in substitution reactions.Contrary to this expectation, acetoxy, propionoxy, isobutyroxy, and pivaloxy are effective in this role.At low temperatures radical chain brominations of alkanes and haloalkanes occur in satisfactory yields when the acyl hypobromites, RCO2Br, are used; the selectivities are independent of the structure of R.Two distinctive hydrogen-abstracting RCO2. are involved in these chain reactions, either the ? or ?_a electronic states; which electronic state is the chain carrier is determined in the step RCO2Br + X. -> RCO2. + XBr.These C_? and C_? radicals resemble tert-butoxy in their hydrogen-abstraction selectivities.The concordance of these results with a state-of-the-art calculation is discussed.