Conformation of α-substituted cycloalkyl radicals

Abstract

Radicals obtained by addition of Et₃Si˙ to the double bond of methylenecycloalkanes have been detected by e.s.r. at low temperature. The three-, four-, five-, and six-membered rings have been investigated. In the last case different splitting constants were detected for axial and equatorial hydrogens at low temperatures whereas a single average value is observed at higher temperatures. In the intermediate range line broadening effects allowed ΔG^‡ 5.2 kcal mol^–1 for the ring reversal process to be developed. In the case of the five-membered ring experimental evidence for a non-planar conformation has been also obtained. On the other hand the four-membered ring seems to be planar, at least within the approximation involved in these determinations.