Prediction of tautomeric equilibria for N-arylamidines

Abstract

The influence of substitution at amidine nitrogen atom on tautomeric equilibria and basicities of N-aryl-amidines is discussed. It is shown that tautomeric equilibrium constants (as pK_T) can be correlated with σ^∘ substituent constants, but measured pK_am values of tautomeric mixture should obey a non-linear relation with σ^∘ constants. The methods of prediction of pK_T value are proposed, and applied to N-aryl-formamidines and acetamidines.