Reactions of OH Radicals in the H–NO2 and H–NO2–CO Systems

A mass-spectrometric study has been made of the stoichiometry of the reactions of OH radicals generated by the reaction H+NO2→OH+NO, under conditions similar to those used in some previous studies of the kinetics of the reactions of OH radicals with each other and with CO. Contrary to previous assumptions, when H atoms are initially in excess over NO2, the reactions 2OH→H2O+O, O+OH→O2+H, OH+CO→CO2+H, do not account completely for the decay of OH. An additional reaction occurs which produces water and is probably the first-order heterogeneous reaction recently postulated on purely kinetic evidence by Breen and Glass [J. Chem. Phys. 52, 1082 (1970)]. When NO2 is initially in excess over H, a fast reaction takes place involving OH radicals and NO2 {as first observed by Wilson and O'Donovan [J. Chem. Phys. 47, 5455, (1967)]}. This is probably the reaction OH+NO2→HNO3.