Predicting rate constants of OH radical reactions with organic substances: advances for oxygenated organics through a molecular orbital HF/6-31G** approach

摘要

The molecular orbital OH (MOOH) approach is a perturbational quantum chemical method to predict rate constants of OH radical reactions with organic compounds. Going beyond previous AM1 parameterizations, a first ab initio implementation employing the HF/6-31G** level of calculation has been developed. For a set of 799 organic compounds with experimental rate constants, k_(OH), varying over more than six orders of magnitude, the new MOOH-HF method is superior to both MOOH-AM1 and Atkinson's increment scheme, yielding a predictive squared correlation coefficient (q~2) of 0.95 and a root-mean-square error of 0.29 log units. For oxygenated compounds, MOOH-HF shows significant improvements over MOOH-AM1, which holds in particular for aldehydes and ketones. The discussion includes detailed comparative analyses of the model performances for individual compound classes.