Comparison between the gas-phase and the solution reaction of the nitrate radical and methylarenes

The reaction between the nitrate radical and methylarenes has been studied in the gas phase. Benzaldehydes, benzyl nitrates, benzylic alcohols, and nitro derivatives have been found as reaction products. The reaction of an intermediate alkoxy radical with oxygen or nitrogen dioxide is suggested as the source of aldehydes and nitrates. The formation of nitro derivatives in the gas-phase reaction is of relevance to the environment. Kinetic isotope effect measurements favor the hypothesis of H-atom abstraction as the rate-determining step. The reaction of methylarenes with photogenerated nitrate radical in solution gives the same reaction products, but the reaction seems to occur via a rate-determining electron-transfer step, involving a radical cation in the transition state.