Acid—base equilibria of 2-furoic acid hydrazide and adipic acid dihydrazide in aqueous—organic media

The acid-base equilibria of 2-furoic acid hydrazide (FAH) and adipic acid dihydrazide (AADH) were investigated by pH measurements in water-dimethylformamide (10:60,vv) and water-dioxane (10:60,vv). The protonation constants were estimated by MINIQUAD75 which employs a non-linear least squares method based on the Marquardt algorithm. The variation in log KM1 (log β011) and log KM2 (log β012 − log β011) for protonation processes against mole fraction were fitted into empirical quadratic models. The number of water molecules released was calculated using a complete equilibrium constant. The stability constants for a few typical systems were compared with SUPERQUAD.