Photo-Fries rearrangements of 1-naphthyl esters in the glassy and melted states of poly(vinyl acetate). Comparisons with reactions in less polar polymers and low-viscosity solvents

Abstract

The photo-Fries and associated photoreactions of four 1-naphthyl acylates have been examined in two types of poly(vinyl acetate) (PVAc) films above and below their glass transition temperatures, T_g. Because of the ‘templating’ effect of the esters on their reaction cavities, especially below T_g, the distributions of photo-Fries products, as mandated by the intermediate acyl/1-naphthyloxyl singlet radical pairs, are determined largely by the initial conformations of the guest molecules. Even above T_g, at 50 °C, where segmental chain motions of PVAc are relatively rapid, the influence of the cages in directing product formation is apparent. The radical-pair recombination rates for formation of the keto precursor of 2-(2-phenylpropanoyl)-1-naphthol upon irradiation of 1-naphthyl 2-phenylpropanoate in PVAc are reduced drastically as the temperature is lowered from above to below T_g. Comparison of results in PVAc with those in low-viscosity solvents (ethyl acetate and hexane) and low-polarity polymer films (polyethylene and polypropylene) indicate that interactions between the radicals produced from irradiation of 1 and the acetate pendant groups of PVAc, as well as the nature of its chain motions above and below T_g, influence enormously the course of the photo-Fries rearrangements.