Computational Analysis of Various Reactions Between Hydroxyl Radicals and Organic Mercury Species

The interactions between hydroxy radicals and both dimethylmercury and methylmercury hydroxide have been studied using ab-initio methods. The density functional theory (DFT) method M06-2X was used to optimize the structures of the stationary points in each reaction channel. The single point energies were determined using coupled-cluster theory (CCSD(T)). For the reaction with dimethylmercury there are three possible channels, with the favored product as methylmercury hydroxide with the smallest energy barrier of 7.3 kcal mol-1 (k(TST)=1.23x10-12 cm3 molecule-1 s-1). For the reaction between hydroxyl radical and methylmercury hydroxide there are six possible channels with the most probable channel being a hydrogen abstraction to form MeHgO radical. This channel has the lowest energy barrier of 2.5 kcal mol-1 with a rate constant of 3.87x10-9 cm3 molecule-1 s 1. Based on these results, dimethylmercury will undergo demethylation due to hydroxyl radicals whereas methylmercury hydroxide will not.