Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

The kinetics and mechanism of oxidation of Cr(II) ions by haloforms were studied in H₂O-CH₃OH-HClO₄ system, in the case of bromoform also in H₂O-CH₃COOH-HClO₄ system. Six mol of Cr²⁺ ions is consumed in the oxidation-reduction reaction per one mol of CHX₃, the final organic product is methane. The primary Cr(III) products are CrX²⁺ ions and [CrCHX₂²⁺] organochromic complexes. The oxidation-reduction reactions are 1st order with respect to each reactant, the rate constants of the 2nd order reaction, independent of the H⁺ ion concentration and the ionic strength, decrease in the order k_I > k_Br > k_Cl. The inner-sphere mechanism is suggested for the electron transfer; the effect of the C-X bond cleavage is more significant than the effect of the Cr-X bond formation and controls the rate of the halogen atom transfer from the haloform to Cr(II).