Estimation of Rate Constants for Reactions of Organic Compounds under Atmospheric Conditions

Structure-activity (SAR) methods are presented for estimating rate constants at 298 K and approximate temperature dependences for the reactions of organic compounds with OH, NO3, and Cl radicals and O-3, and O(P-3) in the lower atmosphere. These are needed for detailed mechanisms for the atmospheric reactions of organic compounds. Base rate constants are assigned for the various types of H-abstraction and addition reactions, with correction factors for substituents around the reaction site and in some cases for rings and molecule structure or size. Rate constant estimates are made for hydrocarbons and a wide variety of oxygenates, organic nitrates, amines, and monosubstituted halogen compounds. Rate constants for most hydrocarbons and monofunctional compounds can be estimated to within & PLUSMN;30%, though predictions are not as good for multifunctional compounds, and predictions for ~15% of the rate constants are off by more than a factor of 2. Estimates are more uncertain in the case of NO3 and O-3 reactions. The results serve to demonstrate the capabilities and limitations of empirical methods for predicting rate constants for the full variety of organic compounds that may be of interest. Areas where future work is needed are discussed.

Automated summary

SAR methods are used to estimate rate constants and temperature dependences for the reactions of organic compounds with different radicals in the atmosphere. The estimates can predict the reactions of most single-functional compounds relatively accurately, but the accuracy is lower for multi-functional compounds, and the estimates for NO3 and O-3 reactions are more uncertain.