Potentiometric investigations of molecular heteroconjugation equilibria of substituted phenol + n-butylamine systems in dimethyl sulfoxide

Molecular heteroconjugation constants, KBHADMSO and KAHBDMSO, expressed as their logarithms, have been determined by potentiometric titration for eleven substituted phenol + n  -butylamine systems in a polar protophilic aprotic solvent, dimethyl sulfoxide (DMSO). An increasing tendency towards molecular heteroconjugation in these systems without proton transfer has been found with increasing pKaDMSO (HA), i.e.  , with decreasing phenol acidity. Moreover, a linear correlation has been established between the determined lgKBHADMSO values and pKaDMSO (HA). Furthermore, overall stability constants, lgKoDMSO, could be correlated linearly with pKaDMSO (HA) values.