A theoretical study of substituent effects on tautomerism of 2-hydroxybenzimidazoles.

The geometries, relative stabilities of some 4(7) and 5(6) substituted 2-hydroxybenzimidazole derivatives were calculated with full geometry optimization using AM1 and PM3 in aqueous phase. With the exception of molecules 4, 6 and 7 for all the 4(7) and 5(6) substituted 2-hydroxybenzimidazole derivatives the 3H and keto forms were found to be favored.