PHOTOCHEMICAL ALPHA-CLEAVAGE REACTION OF BENZOIN AND ITS DERIVATIVES

The quantum yields of alpha-cleavage type photodissociation (Phi(r)) w ere determined for benzoin, alpha-phenylbenzoin and alpha-phenylbenzoi n methyl ether by measuring the transient absorbance of the product ra dicals using a nanosecond laser flash photolysis technique. The dissoc iation yields are 0.25-0.35, which are close to the alpha-cleavage yie lds of other aryl and alkyl ketones in the n pi excited state. The lo west excited singlet and the low-lying triplet states are assigned to the n pi type electronic states according to the absorption and phosp horescence measurements. The assignment agrees with the fact that the dissociation yields of these benzoins are relatively high. (C) 1998 El sevier Science S.A. All rights reserved.