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.