Liquid phase oxidation of acetophenone to phenylglyoxal by selenium dioxide alone or with aqueous nitric acid

The liquid phase oxidation of acetophenone to phenylglyoxal using selenium dioxide was carried out at 90°C in dioxane or ethyl alcohol with 10% (v/v) of water as a solvent with a 2:1 molar ratio of acetophenone to selenium dioxide. The yield of phenylglyoxal was more than 98% based on acetophenone and the efficiency of utilisation of selenium dioxide was as high as 99%. A novel process version based on the oxidation of acetophenone by aqueous nitric acid in the presence of selenium dioxide as a selective catalyst in a redox cycle was also considered with a view to changing the use of selenium dioxide as a stoichiometric oxidising agent to that of a catalyst, and it was found to be attractive.