The radical addition of N-haloamides to 1,6-heptadiene: The transfer step in the photochemical and chromous chloride promoted addition of N-haloamides to olefins

Abstract

A study of the photochemical addition of N-haloamides (ZCONHX) to 1,6-heptadiene shows that the reactivity of ZCONHX as an halogen-atom donor to an alkyl radical increases with Z in the order CH3 < ClCH2 < OC2H5 ≤ CCl3 ∼ CF3 which indicates a polar character of the transition state. An N-bromoamide is shown to be more reactive than an N-chloroamide as expected. The chromous chloride promoted addition of N-chlorochloroacetamide and N-chlorotrichloroacetamide to 1,6-heptadiene is compared with the photochemical addition under similar conditions of solvent and temperature. The better interpretation of the results, for the chromous chloride promoted additions, is in ternis of a classical chain mechanism rather than a redox chain mechanism; the latter mechanism cannot be excluded however.