Reaction Paths for Aqueous Decomposition of CCl2

The potential energy surface (PES) for the H 2 O + CCl 2 reaction was investigated at the ab initio SCF and MP2 levels of theory, employing the DZP basis set, in order to determine the mechanism of basic aqueous decomposition of CCl 2 . Several possible pathways were considered, including reactions with other H 2 O molecules and OH - . We have found that the first step corresponds to insertion of CCl 2 into the O−H bond of water, resulting in the CHCl 2 OH species. This molecule loses HCl in one elimination reaction catalyzed by OH -, forming ClCHO. Again, OH - catalyzes the elimination of other HCl, resulting in CO, the decomposition product. The first step is the slow one, and we have used transition-state theory to estimate the rate constant for the aqueous decomposition of CCl 2 . The obtained rate constant was used for building a general picture of CHCl 3 decomposition in basic aqueous solution. The results of the present study are in agreement with experimental observations.