Electron spin resonance study of inversion and conformations in 1-hydroxycyclohexyl radicals

Abstract

We have obtained the variable-temperature e.s.r. spectra of the 1-hydroxycyclohexyl, 4-methyl-1-hydroxycyclohexyl, and 4-t-butyl-1-hydroxycyclohexyl radicals by photolysis of the precursor alcohols mixed with di-t-butyl peroxide. From computer analysis of the observed linewidth alternation in the spectra of the first two radicals, we calculate activation energies for chair-to-chair inversion to be 6.6 and 11.4 kcal mol^–1, respectively. In order successfully to fit the spectra from the 4-methyl radical it was necessary to include the axial–equatorial energy difference of 1.8 kcal mol^–1. The radical sites are probably non-planar and both the radical sites and the rings invert during the hindered motion.