Termination reactions of C5–C12 cycloalkyl radicals and carbenes

Abstract

Reactions of C₅–C₁₂ cycloalkyl radicals and carbenes produced during radiolysis, vacuum-u.v. photolysis, and decomposition of cycloalkanone p-tosylhydrazones were investigated. The disproportionation to combination ratios of radicals are ca. 1 and agree with the ratios of linear secondary radicals. The disproportionation of smaller cycloalkyl radicals yields cis-cycloalkenes and cycloalkanes; from C₉ and C₁₀cis- and trans-cycloalkenes and cycloalkanes and from C₁₁ and C₁₂trans-cycloalkenes and cycloalkanes are produced. Both atoms of H₂ given off in the elimination reaction from excited cycloalkane molecules originate from the same carbon atom and in this process carbenes are formed. Rearrangement of small (C₅, C₆) and large (C₁₁, C₁₂) cycloalkylcarbenes in the solvent of the given cycloalkane occurs by 1,2-hydrogen migration. C₇–C₁₀ carbenes rearrange both by hydrogen atom migration and transannular insertion.