The mechanism of the primary process in the photoreduction of aromatic carbonyl compounds

Abstract

Experimental data concerning the temperature dependence of the rate constants and the deuterium kinetic isotope effects on the photochemical hydrogen-abstraction reaction of aromatic ketones and quinones show that nuclear tunnelling is not important in the primary process, which is best described as a thermally activated reaction of the electronically excited molecule. The kinetics of the primary photochemical process are controlled by the activation barrier, which is made up of at least three contributions related to the bond strength of the hydrogen atom donor, to the bond strength of the excited carbonyl molecule and to an electrostatic interaction of the partners.