Conformation of α-substituted cycloalkyl radicals

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.