Photochemistry of phenyl phenylacetates adsorbed on pentasil and faujasite zeolites

The photochemistry of phenyl phenylacetate 1, p-tolyl phenylacetate 2, o-tolyl phenylacetate 3 and phenyl o-tolylacetate 4 was investigated both in homogeneous solution and adsorbed on ZSM-5 and NaY zeolites. Photolyses of these esters in acetonitrile result in photo-Fries rearrangement products, phenols and diphenylethane as well as phenyl benzyl ethers. In contrast, photolyses of these esters adsorbed on NaY zeolite only give the ortho Fries rearrangement products. On the other hand, the photochemical reaction of 1 and 2 adsorbed on ZSM-5 zeolite only produces toluene and phenols, while under identical conditions the photochemical products for 3 and 4 are the Fries rearrangement and decarbonylation products. The product distributions for these esters adsorbed both on ZSM-5 and NaY zeolites are different from those for dibenzyl ketones as reported in the literature. All of these observations are interpreted in terms of (a) the size and shape sorption selectivity of ZSM-5 zeolite, (b) restriction of diffusional and rotational mobility of the radical pair imposed by the zeolite surface and (c) the multiplicity of the excited state responsible for the homolytic bond cleavage.