Quantum chemical study of the substituent effect on pKa of molecules with conjugated bonds using the PPP method

It is shown that the change of pK_a of unsubstituted heterocyclic compounds on substitution is proportional to the difference of the residual -electron charges at the position where the functional group is introduced in the unsubstituted heterobase and its conjugated acid.Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 24, No. 1, pp. 13–20, January–February, 1988.The author expresses his gratitude to M. M. Mestechkin and N. G. Korzhenevskaya for the discussion.