Solvent effect on the decarbonylation of acyl radicals studied by laser flash photolysis

Abstract

Absorption spectra of transient radicals generated from dibenzyl and di-tert-butyl ketones and rate constants for their fragmentation and termination reactions were obtained by laser flash photolysis in various solvents. Whereas the pivaloyl radical absorbs only for λ⩽ 240 nm, the first absorption band of phenylacetyl is red shifted which is ascribed to a phenyl–carbonyl conjugation. The rate constant for the decarbonylation of the acyl radicals decreases markedly with increasing solvent polarity. This is explained by the dipole moment which decreases during the scission process.