Spectrophotometric study of basicity of some substituted alpha-(benzamidomethyl)phenylhydrazines

Abstract

The protonation behavior at 25 degrees C in water and in aqueous sulfuric acid solutions of some substituted alpha-(p-R-benzamidomethyl)phenyl hydrazines (R=H, CH3, Cl, Br) was investigated by UV spectrophotometry. The absorption spectra in sulfuric acid solutions were analyzed by the method of multivariate analysis. The protonation constants of hydrazine (pK(1)) and amide (pK(2)) moieties were determined; pK(2) values were calculated from the reconstituted absorption spectra by Cox - Yates method. Dependence of pK(2) on Hammetts sigma constants was discussed.