Potentiometric Study of Acid-Base Interactions in Acetonitrile

The potentiometric titration curves of acids of different types were studied using piperidine and tetra-n-butylammonium hydroxide, (Bu4NOH), as titrants in acetonitrile (AN) as solvent. The effect of methanol addition on the shape of the potentiometric curves was discussed. The dissociation constants, KHA, and homoconjugation constants, KHA2- , of some acids were potentiometrically determined in AN. No exact correlation was found between KHA of the studied acids in AN and the corresponding values-in water. It was concluded that the acid characteristics, its anion properties, and the solvent . type are the most important factors determining KHA2-. The heteroconjugation constants, KAHA,- of some anions with different acids were also determined. K AHAc values for some substituted benzoic acids with reference to acetate ion were found to follow a linear free energy relationship with Hammett substituent constants