Studies on the oxidative cleavage of the CC triple bond during the Autoxidation of Acetylenic Hydrocarbons 1. Evidence for α‐dicarbonyl compounds as intermediates

Abstract

Examination of oxidation mixtures of 1‐phenylprop‐1‐yne, 1‐phenylbut‐1‐yne and 1‐phenyl‐3‐methylbut‐1‐yne revealed the presence of hitherto not reported interesting products, especially the α‐dicarbonyl compounds 1‐phenylpropane‐1,2‐dione, 1‐phenylbutane‐1,2‐dione and 1‐phenyl‐3‐methylbutane‐1,2‐dione respectively in minor quantities. Some other typical products like benzil, benzoic anhydride and phenyl benzoate were also characterized. Although the oxidation of diphenylacetylene is very slow, benzil could be found as the main detectable product along with traces of benzoic acid. The α‐diketones corresponding to the 1‐phenylalk‐1‐ynes were oxidized at 110°C. In each case benzoic acid and the lower carboxylic acids as in the case of the autoxidation of the corresponding acetylenes were obtained. Benzil, benzoic anhydride and phenyl benzoate were also characterized in all the cases. Therefore, α‐diketones are considered as intermediates responsible for the formation of the oxidative cleavage products of the CC triple bond.