Abstract
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.
