Metal Complexes of Isonicotinoylhydrazine and Related Compounds. II. Acid Dissociation Constants and Ultraviolet Absorption Spectra of Isonicotinoylhydrazine and Related Compounds.

Acid dissociation constants of isonicotinoylhydrazine (INH) and seven related compounds were determined by means of pH titration (ionic strength 1.0). Values of pKa obtained were as follows : INH : 2.13, 3.81, 11.03. nicotinoylhydrazine (NH) : 2.26, 3.63, 11.49. picolinoylhydrazine (PH) : 1.26, 3.07, 12.25. benzoylhydrazine (BH) : 3.27, 12.53. p-nitrobenzoylhydrazine (PNBH) : 2.90, 11.28. isonicotinamide (INA) : 3.82. 1-isonicotinoyl-1-methylhydrazine (N-Me-INH) : 1.03, 4.17. 1-isonicotinoyl-2-methylhydrazine (N'-Me-INH) : 2.46, 4.04, 10.96. The ultraviolet spectra of these compounds at various pH were measured, and the results showed a good parallelism with the pKa values. Some informations about their structures in aqueous solutions were obtained from the spectral data.