Photochemistry of Acetanilide. II. The Primary Processes in the Photochemical Reaction

Abstract

Abstract The photochemical primary processes of acetanilide have been discussed on the basis of the quantum yields in various solvents, the dependences of the quantum yields on the excitation wavelength, and the emission spectra. The quantum yields of the products (o-aminoacetophenone and p-aminoacetophenone) at 2537 Å decreased greatly in polar solvents. A non-linear relationship between the quantum yield and the fraction of hydrogen-bonded acetanilide in the cyclo-hexane-ethanol solution was obtained. No variation in the quantum yield was observed upon the change of the excitation from 2537 to 2740 Å. These results indicate the occurrence of a radiationless internal conversion, S1(ππ*)←S2(ππ*). The relative fluorescence intensity in a polar solvent was larger than that in a nonpolar solvent. On the basis of these studies, it can reasonably be considered that the primary process in the photochemical reaction of acetanilide involves predissociation.