Reactivity of polychlorinated biphenyls in nucleophilic and electrophilic substitutions

•Quantum chemical calculations were carried out for PCBs congeners.•Calculated descriptors were used to explain the PCBs reactivity in SN and SE substitutions.•Obtained data were used to estimate the PCBs reactivity in the SN reactions.•Calculated descriptors were insufficient to explain the PCBs reactivity in the SE reactions.•New neutralization methods of the large-capacity PCBs were discussed. To explain the chemical reactivity of polychlorinated biphenyls in nucleophilic (SN) and electrophilic (SE) substitutions, quantum chemical calculations were carried out at the B3LYP/6-31G(d) level of the Density Functional Theory in gas phase. Carbon atomic charges in biphenyl structure were calculated by the Atoms-in-Molecules method. Chemical hardness and global electrophilicity index parameters were determined for congeners. A comparison of calculated descriptors and experimental data for congener reactivity in the SN and SE reactions was made. It is shown that interactions in the SN mechanism are reactions of the hard acid–hard base type, these are the most effective in case of highly chlorinated substrates. To explain the congener reactivity in the SE reactions, correct descriptors were not established. The obtained results can be used to carry out chemical transformations of the polychlorinated biphenyls in order to prepare them for microbiological destruction or preservation.