Mechanistic study of the photolysis of ring-substituted benzyl alkanoates in methanol

The photochemistry of ring-substituted benzyl alkanoates, 1a-g and 2a-g, ha s been examined in methanol (MeOH). The eater conversions were substituent independent, whereas the yields of ionic products were strongly dependent. The fluorescence quantum yields and lifetimes for all methoxybenzyl eaters, except para-isomers, decreased remarkably in acetonitrile (MeCN) and MeOH, Semiempirical MO calculations for the excited-state esters demonstrated th at the charge densities of methylene carbon in ortho- and meta-isomers are markedly changed in the excited singlet state, which could explain the subs tituent dependence on the ionic product yields and the emission properties. A satisfied mechanistic interpretation of the ion formation prefers the he terolysis pathway that has been proposed by Zimmerman et al. [1-3]. (C) 200 1 Elsevier Science B.V. All rights reserved.