Enolization in radical cations of o-methylacetophenone and related species under cryogenic conditions

Abstract

Upon radiolytic ionization of o-methylacetophenone in low temperature matrices, the radical cation of the corresponding enol is formed. The kinetics of this process indicate a significant contribution of quantum-mechanical tunnelling in the hydrogen atom transfer. The same species is also formed by ionizing 1-methyl-1,2-dihydrobenzocyclobutenol but the composition of the rotameric mixture of enol radical cations is different in this case. Analogous experiments with 5,8-dimethyl-1-tetralone demonstrate that enol radical cations are stable in their Z-conformation under cryogenic conditions in contrast to the corresponding neutrals.