Photochemistry of α-oxo-oximes. Part 5. Photolysis of 3-ethoxyiminobutan-2-one

Abstract

The photolysis of 3-ethoxyiminobutan-2-one (1) with λ 254 nm has been investigated using cyclohexane and acetonitrile as a solvent. Photo-excited (1) undergoes N–O bond homolysis with formation of an α-oxo-iminyl and an ethoxyl radical. The α-oxo-iminyl radical undergoes β-scission with formation of acetonitrile, or recombines with an acetyl radical to yield the N-acetyl-α-oxo-imine (17). Mechanisms for the photoformation of a number of the nitrogen containing products from this presumed intermediate (17) are proposed. The ethoxyl radicals yield formaldehyde, acetaldehyde, ethanol, and butane-2,3-dione. A correlation between the amounts of these products, based on the reaction steps proposed for their formation, was found to hold for the initial stages of the photolysis. In acetonitrile as solvent 77% of the ethoxyl radicals disproportionate, 18% react by hydrogen abstraction, and 5% by β-scission.