Estimation of rate coefficients and branching ratios for gas-phase reactions of OH with aliphatic organic compounds for use in automated mechanism construction

摘要

Reaction with the hydroxyl (OH) radical is the dominant removalprocess for volatile organic compounds (VOCs) in the atmosphere. Ratecoefficients for reactions of OH with VOCs are therefore essential parametersfor chemical mechanisms used in chemistry transport models, and are requiredmore generally for impact assessments involving the estimation of atmosphericlifetimes or oxidation rates for VOCs. Updated and extendedstructure–activity relationship (SAR) methods are presented for the reactionsof OH with aliphatic organic compounds, with the reactions of aromaticorganic compounds considered in a companion paper. The methods are optimizedusing a preferred set of data including reactions of OH with 489 aliphatichydrocarbons and oxygenated organic compounds. In each case, the ratecoefficient is defined in terms of a summation of partial rate coefficientsfor H abstraction or OH addition at each relevant site in the given organiccompound, so that the attack distribution is defined. The information cantherefore guide the representation of the OH reactions in the next generationof explicit detailed chemical mechanisms. Rules governing the representationof the subsequent reactions of the product radicals under troposphericconditions are also summarized, specifically their reactions withO2 and competing processes.