Acid Catalyzed Hydrolysis Report

The kinetics of the acid catalyzed hydrolysis reaction of five Fe(II) Schiff base amino acid complexes were followed spectrophotometrically at 298 K. The used ONO donor ligands were derived from the condensation of salicylaldehyde with different five amino acids. The acid catalyzed hydrolysis reaction was studied in different ratios (v/v) of aqua – organic mixtures and in the presence of different concentrations of surfactants (CTAB and SDS). The increase in organic solvent ratio enhances the reactivity of the reaction. Moreover the addition of CTAB or SDS to the reaction mixture accelerates the reaction reactivity. The obtained kinetic data were used to determine the values of mG (the change in the activation barrier) for the studied

The decrease in CMC value of the surfactant in presence of the complexes suggesting the interaction between the surfactant and the chelates which bring the reactants together through electrostatic interactions[31]. As the ionic micelles enhance the rate of reactions by increasing the concentration of the reactants within the small volume of its Stern layer[45]. Micelles can affect the reaction rates by including the reactants into the micellar aggregate. It was observed that the reaction rate increases with increasing both [CTAB] and [SDS] (Figs. 8 & 9), which clearly showing the catalytic effect of both CTAB and SDS below and above their CMC values[37, 46, 47]. It is can be demonstrated that the addition of CTAB and SDS to the reaction mixture, affected the hydrophobicity of the studied complexes leading to the acceleration in the reaction rate. The interaction between the surfactants and the complexes decreases the surface area of the reactants and increases the reaction rates, as the presence of the micelles leads to change in the mutual attraction and repletion force in the reaction medium. Therefore, the collision rate between the reactants will increase because of their nearby distance at the micellar boundary[37], this trend may considered as surface catalysis. Thus the attraction of the reactants species on the micellar surface enhances the reaction rate. On increasing [surfactant], the total area available for reaction will be more[30], consequently the observed rate constant (kobs.) values increase with increasing [surfactant] (cf. Tables.4 & 5). The plots of kobs against [surfactant] (Figs. 8 & 9) show a gradual increase in rates with [surfactant]. Such a type of behavior of the studied surfactants may be due to