Photolysis of Acetic Anhydride

Abstract

The photolysis of acetic anhydride has been studied using a hot mercury arc at temperatures from 60° to 160°C by analysis of the gaseous products. CO and C2H6 are produced at equal rates which are one-half the rate of production of CO2. At 60°C, CO production is delayed initially but in time reaches the same rate as C2H6. Using acetone as actinometer, the quantum yield of CO2 is two, of CO and C2H6, unity. The decomposition of acetic anhydride can be photosensitized by acetone. Mass-spectral analysis of the liquid residue at 160°C showed the absence of acetone, biacetyl, methyl acetate, acetylacetone, and acetonyl acetone. A fragment of mass 57, increasing in intensity with duration of reaction was present in amounts sufficient to account for a material balance. Some steps in the mechanism are discussed.