Acceleration Effect of Fe(II), Co(II), Ni(II) and Cu(II) on the Hydrolysis Rate of Ortho or Para-Hydroxy Schiff Bases

Article abstract of DOI:10.1002/jccs.199800123

The kinetics of hydrolysis of ortho- or para-hydroxybenzylidene-4-benzidine Schiff bases have been examined in the pH range 1.70-11.90, in aqueous media containing 20wt% dioxane, at 20°C. In basic media, pH > 8.47, a slight increase in the hydrolysis reaction rate of the Schiff bases is observed. In such basic media, the rate-controlling step is the attack of hydroxide ion on the ionized Schiff base. Below pH 6.82, the rate-determining step is ascribed to be the attack of water molecules on the protonated substrate. The effects of Fe(II), Co(II), Ni(II) and Cu(II) ions on the hydrolysis reaction rate of the Schiff bases have been studied and discussed on the basis of formation of a monocyclic chelate rings. The various thermodynamic parameters have also been evaluated and discussed.