A kinetic and equilibrium study of the reaction of glycine with chromium(III) in aqueous solution

Abstract

The formation of tetra-aquaglycinatochromium(III) from glycine and chromium(III) has been studied at pH = 3.0–3.8, 40–54 °C, and I= 0.4 mol dim^–3(NaClO₄). The equilibrium constant (log₁₀K₁) is 7.60 at 44.8 °C. The reaction obeys the rate equation k_obs.=k+k′[H⁺]^–1 and under all the conditions studied is zero order in the concentration of glycine. A mechanism involving extensive outer-sphere complexation of hexa-aquachromium(III) and its conjugate base is proposed. The activation parameters are compared to literature values.