Some new views on the tautomerisation mechanism

Published data on the prototropic tautomerism of some carbonyl and nitrogen-containing acyclic and heterocyclic compounds are systematised. Mechanisms of intramolecular and intermolecular proton transfer in tautomerisation reactions are considered. On the basis of the results of semiempirical and ab initio quantum-chemical calculations, preference is given to an intermolecular collective (dimeric, trimeric, tetrameric or oligomeric) mechanism. A new approach to the description of the solvent effect on the prototropic tautomeric equilibrium is proposed. The bibliography includes 107 references.