Photochemical α-cleavage reaction of benzoin and its derivatives

Abstract

The quantum yields of α-cleavage type photodissociation ( Φ r) were determined for benzoin, α-phenylbenzoin and α-phenylbenzoin methyl ether by measuring the transient absorbance of the product radicals using a nanosecond laser flash photolysis technique. The dissociation yields are 0.25–0.35, which are close to the α-cleavage yields of other aryl and alkyl ketones in the nπ* excited state. The lowest excited singlet and the low-lying triplet states are assigned to the nπ* type electronics states according to the absorption and phosphorescence measurements. The assignment agrees with the fact that the dissociation yields of these benzoins are relatively high.