Acid-base strengths in pyridine

M. Bos, E.A.M.F. Dahmen

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    Although pyridine is a solvent with a low dielectric constant, spectrophotometric determinations show simple dissociation without ion pairs as intermediates for some sulfonphthaleins and polynitrophenols in pyridine.

    The salts of a number of amines and hydrochloric acid, perchloric acid and picric acid are not completely dissociated in pyridine. Dissociation constants of these salts were determined from differential vapour pressure measurements. For the titrations in pyridine of an acid with an amine, calculations were based on the following reactions : HX∡H+ + X−; B + H+ ∡BH+; BH+ +X−∡BH+X−. With this reaction scheme it was possible to determine pKa values for protonated amines in pyridine from the curves of titrations carried out with a calibrated glass electrode. Evidence for the occurrence of homoconjugation of some polynitrophenols in pyridine was found in the titration of these compounds with tetramethylguanidine. Homconjugation constants were estimated from the titration curves.
    Original languageEnglish
    Pages (from-to)39-46
    JournalAnalytica chimica acta
    Issue number1
    Publication statusPublished - 1971


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