Investigation Od Acid-Base Properties of Aromatic Hydrazones in Basic Media at Constant Ionic Strength

Abstract

Abstract. UV spectroscopic methods were used in order to determine dissociation constants of some aromatic hydrazones. The acid-base properties of investigated hydrazones were followed in sodium hydroxide media at constant ionic strength of 0.5 mol/dm 3 adjusted with sodium perchlorate. Absorption band with the maximum of 330 nm was noticed in neutral media. A batochromic shift of this band was observed in basic media, probably due to the dissociation process. The dissociation process took place in one step for four investigated hydrazones and in two steps for the hydrazone with a phenol group in its molecule. The absorbance data from the UV spectra were used for the calculation of dissociation constants. The obtained pKHA values were between 2.11 and 2.62 which suggested that the influence of the substituents is not significant. At the same time, pKHA values were determined graphically from the intercept of the dependence of logI on pH. There are no important differences between calculated and graphically determined dissociation constant values.