QSAR prediction of ozone tropospheric degradation

The lifetime of organic chemicals in the atmosphere can be calculated from a knowledge of the rate constant of their reaction with free radicals (OH(.), NO(3).) and O(3). The rate constant for the tropospheric degradation of 125 organic compounds by reaction with ozone, the least widely and successfully modelled degradation process, is predicted here by MLR-QSAR modelling based on a variety of theoretical molecular descriptors, selected by the Genetic Algorithm-Variable Subset Selection (GA-VSS) procedure. The proposed models, checked for their reliability and robustness, have good predictivity, verified by internal (Q(LMO(50%))(2) 82 - 88%) and also external validation (Q(EXT)(2) = 90%). The best splitting of the original data set into representative training and test sets has been obtained by the Experimental Design approach. The model applicability domain was always verified by the leverage approach. The average root-mean square error (RMS) for the prediction of log k(O3) was 0.73, similar to the typical range of experimental error.