Experimental and theoretical studies on the mechanism of 1,2‐migration of vinyl and formyl substituents in free radicals

Vinyl and formyl groups undergo rearrangements of the type XCH  CMe 2  ĊH 2 → ĊMe 2  CH 2  CHX (XCH 2 or O) with comparable rates (10 6  10 7 l/mol · s, 20°C). This result is in line with high‐level ab initio calculations performed on the basic systems, i.e. XCH  CH 2  ĊH 2 , which give barriers of activation of 14.9 (CH 2 CH  CH 2  ĊH 2 ) and 19.2 kcal/mol (OCH  CH 2  ĊH 2 ), respectively. The calculations suggest that the rearrangements proceed via cyclopropane‐like intermediates.