Investigations of Reactions of Selected Azaarenes with Radicals in Water. 1. Hydroxyl and Sulfate Radicals

The oxidative degradation of binuclear azaarenes is studied in a number of environmentally relevant radical reactions. The comparison between oxidation mechanisms of hydroxyl and sulfate radicals, as well as between dark and photoreactions, is done. Most of the products formed are identified. With the change from dark to photoreactions of quinoline and isoquinoline, a shift of the oxidation center from the benzene to the pyridine rings is observed. The reaction behavior of the benzodiazines can be derived from the reaction patterns of quinoline and isoquinoline. The rate constants of second order are determined for the reactions of the azaarenes with carbonate radicals. The rate constants and the differences in the products formed conformably prove the importance of the inclusion of excited states in the reaction mechanism. The application of the frontier orbital concept allows an easy interpretation. Electron transfer reactions resulting in radical oxygen species are shown to be product determining in direct photolysis, too.