The kinetics and mechanism of gas-phase N-oxidation of pyridine with hydrogen peroxide

The kinetics of N-monooxidation of 4-vinylpyridine as a pi-deficient heteroaromatic compound under the conditions of gas-phase free-radical chain oxidation was studied. The experimental interference kinetic curves of synchronous hydrogen peroxide decomposition and 4-vinylpyridine N-oxidation reactions were obtained. The region of selective N-oxidation was determined and optimum conditions of N-oxide preparation found. The most probable mechanism was suggested. According to this mechanism, a key role in the free-radical N-oxidation of the substrate and its synchronization with the H2O2 decomposition reaction was played by HO2 radicals.