Kinetic Studies of the Hydrolysis of Furfurylidenefuroyl Hydrazone Derivatives, Solvatochromism and Fluorimetric Determination of Iron (III)

Preferential solvation of di-2-pyridylketonebenzoyl hydrazone was investigated in aqueous-ethanol binary mixtures. The kinetics and mechanism of the hydrolysis of a series of substituted furfurylidenefuroyl hydrazones (X-FFH)  in  25% (v/v) ethanol-buffer mixtures have been studied by ultraviolet visible spectrophotometry at different temperatures in the range 22-500C. The hydrolysis reactions were found to follow first-order kinetics. The effect of pH, molecular structure and temperature on the rate of hydrolysis have been discussed. A mechanism for the hydrolysis is postulated in which the attack of water on the protonated substrate is subject to general acid-base catalysis using HCl-sodium acetate buffer solution. The hydrolysis of 5-Chlorothiophenylidene salicoyl hydrazone (CTSH) was found to obey specific acid catalysis using HCl-KCl buffer solutions. The observed rate constants and the catalytic rate constants with respect to H+, HC2O4- and H2C2O4 were calculated. Activation energy and thermodynamic parametres for the hydrolysis are evaluated and discussed. A sensitive method for the determination of iron (III) in trace levels using fluorescence spectroscopy was devised. The method is based on the oxidation of di-2-pyridylketonebenzoyl hydrazone by hydrogen peroxide whereby Fe (III) shows an inhibition effect on the emission signal. The detection limit of Fe (III) was found to be 3.0x10-6M. Interference studies and order of addition were also investigated.  The method was successfully applied to milk and other medicinal samples.