Benzoin, an organic compound with phenyl groups and hydroxyl and ketone functional groups, is readily oxidized by nitric acid to benzil, a diketone. The nitric acid is reduced to nitrous acid, which decomposes into oxides of nitrogen and water. Overall, the reaction converts two molecules of benzoin into two molecules of benzil, along with nitric oxide, nitrogen dioxide, and water.

1. Benzoin is an organic compound consisting of an ethylene bridge flanked by phenyl
groups and with hydroxyl and ketone functional groups: PhCH(OH)-C=O-Ph Nitric acid readily
oxidizes benzoin to benzil (1,2-diphenyl-1,2-ethanedione), a diketone, itself being reduced to
“nitrous acid” which decomposes to oxides of nitrogen + water Ph-CH(OH)-C(=O)-Ph ------[O]-
-----> Ph-CO-CO-Ph HNO3 ? HNO2 + [O] 2 HNO2 ? NO2 + NO + H2O Overall:
2PhCH(OH)-C=O-Ph + 2HNO3 ? 2Ph-CO-CO-Ph + NO2 + NO + H2O
Solution
Benzoin is an organic compound consisting of an ethylene bridge flanked by phenyl
groups and with hydroxyl and ketone functional groups: PhCH(OH)-C=O-Ph Nitric acid readily
oxidizes benzoin to benzil (1,2-diphenyl-1,2-ethanedione), a diketone, itself being reduced to
“nitrous acid” which decomposes to oxides of nitrogen + water Ph-CH(OH)-C(=O)-Ph ------[O]-
-----> Ph-CO-CO-Ph HNO3 ? HNO2 + [O] 2 HNO2 ? NO2 + NO + H2O Overall:
2PhCH(OH)-C=O-Ph + 2HNO3 ? 2Ph-CO-CO-Ph + NO2 + NO + H2O