Kinetics of the Reaction between Copper(II)-Ethylenediaminetetra-acetate Complex and Cyanide

The reaction between copper(II)-ethylenediaminetetra-acetate complex and cyanide ion has been investigated by measuring the change of the polarographic diffusion current of the complex as a function of time after the initiation of reaction. The rates of the reaction obtained with various concentrations of Cu(II)-EDTA complex, cyanide and unchelated EDTA showed that the reaction is of second order on the concentration of the Cu(II)-EDTA complex, fourth order on that of the cyanide and first order on the reciprocal of that of the unchelated EDTA. The reaction mechanism proposed is (Remark: Graphics omitted.) and the rate of the reaction is expressed as (Remark: Graphics omitted.) The value of k1k3/k2 was determined to be 6.8×107 1.4 mole−4sec.−1 in a carbonate bicarbonate buffer of pH 10.0, at ionic strength 0.5 and at 25°C.