THE PHOTOOXIDATION OF AZOMETHANE. III

Abstract

It is confirmed that the yields of all products in the photooxidation of azomethane at relatively high oxygen pressure depend on conversion in a manner which would be explained if a reactive hydrogen donor were produced in the early stages of the reaction. Evidence is presented which indicates that formaldehyde cannot be active as an inhibitor in the system at 162 °C. It is suggested that methyl radicals react with oxygen in two ways. The third order formation of methyl peroxy radicals leads to methoxy radicals and, eventually, to methanol, while the bimolecular reaction between methyl radicals and oxygen leads to a vibrationally excited state of formaldehyde. The latter is thought to undergo oxidization to performic acid, which acts as the inhibitor in the system. Yields of formaldehyde, of nitrogen in excess of that formed in the primary process, and of nitrous oxide are linearly related regardless of the conversion up to about 4%. Methanol is a major product of the oxidation and, if account is taken of its yield, a carbon balance of the order of 90% is obtained.