Ab-initio simulation of radical reactions in the atmosphere

The reaction with OH radicals is the most important sink for organic compou nds in the atmosphere. Hence the rate constant of this reaction is used as a criterion for judging the lifetime of organic pollutants under atmospheri c conditions. The experimental determination of this rate constant is very expensive and time-consuming which has motivated the theoretical investigat ion of such reactions. The aim of the present Car-Parrinello molecular dyna mics study was to determine possible reaction pathways in various systems. Examples for abstraction mechanisms and addition mechanisms are presented. No indication for the textbook statement that OH radicals react in an elect rophilic manner could be found. On the basis of our results we propose an a lternative way for explaining e.g., the extremely fast reaction of OH radic als with amines.