In order to comprehend the data on reactivity of polychlorinated biphenyls of the Sovol mixture in nucleophilic substitution reactions we have performed quantum-chemical simulation using the RB3LYP\6-31G(d) gas phase approximation. Using the “Atoms-in-Molecules” approach, we have computed charges on the biphenyl carbon atoms adjacent to chlorine; furthermore, absolute chemical hardness and global electrophilicity index have been determined for the studied chlorobiphenyls. The calculated descriptors have been correlated with experimentally determined reactivity of the biphenyls in the hard acid-hard base nucleophilic reactions. The higher reactivity of more chlorinated substrates has been confirmed.