Metabolic Electron Attachment as a Primary Mechanism For Toxicity Potentials of Halocarbons

We have carried out systematic large-basis set quantum chemical computations at Møller- Plesset second-order perturbation (MP2) and couple cluster singles + doubles CCSD and CCSD(T)with triples correction levels of theories on a set of 55 halogenated carbons in the Crebelli toxicological dataset. We have computed a number of electronic properties at optimized geometries such as vertical electron affinities, HOMO-LUMO gaps, dipole moments, etc. We have provided insights into the mechanism of toxicity through electron attachment in metabolic pathways by binding to an electron donating enzyme in hepatocytes. The electron transfer from the enzyme to the halocarbon is accompanied by bond elongation resulting in autodetachment as evidenced from potential energy surfaces of the anion and neutral molecule. The autodetachment process leads to production of highly reactive free radicals, which cause tissue damage, and prolonged exposure can result in hepatocellular carcinoma depending on the hydrogen extraction propensity of the free radical and vertical electron affinity of the neutral halocarbon.