Dechlorination pathways of diverse chlorinated aromatic pollutants conducted by Dehalococcoides sp. strain CBDB1

Dechlorination of chlorinated aromatic pollutants (CAPs) has become a major issue in recent decades. This paper reported a theoretical indicator for predicting the reductive dechlorination pathways of polychlorinated dibenzo-p-dioxins (PCDDs), chlorobenzenes and chlorophenols transformed by Dehalococcoides sp. strain CBDB1. Density functional theory (DFT) calculations were carried out at the B3LYP/6-31G(d) level for all related CAPs and Mulliken atomic charges on chlorine atoms (Q_Cl(n)) were adopted as the probe of the dechlorination reaction activity. Q_Cl(n) can consistently indicate the main dechlorination daughter products of PCDDs, chlorobenzenes and chlorophenols conducted by strain CBDB1. The dechlorination reaction favors elimination of the chlorine atoms having greater Q_Cl(n) values. The chlorine atom with the greatest Q_Cl(n) value tends preferentially to be eliminated, whereas the chlorine atom with the smallest Q_Cl(n) value tends unlikely to be eliminated or does not react at all. For a series of compounds having similar structure, the maximal Q_Cl(n) of each molecular can be used to predict the possibility of its daughter product(s). In addition, the difference (ΔQ_Cl(n)) between the maximal Q_Cl(n) and the next maximal Q_Cl(n) of the same molecule can be used to assess the possibility of formation of multiple dechlorination products.