Chlorochromate ion as a catalyst for the photodegradation of chloroform by visible light

Abstract

Exposure of solutions of tetrabutylammonium chlorochromate in chloroform to UV or blue light causes decomposition of the chloroform and the buildup of HCl and peroxides in solution. The CrO₃Cl⁻ is converted during irradiation to CrO₂Cl₂, which forms a suspension in the chloroform, and then to CrOCl₄⁻. CrO₂Cl₂ does not by itself catalyze photodecomposition. The initial rate of HCl formation shows an apparently linear dependence on the incident light intensity and on the fraction of light absorbed by chlorochromate, but different values for the apparent quantum yield at 435 nm with high and low concentrations imply a nonlinear contribution to the rate. It is proposed that, at least initially, a cycle involving photoreduction of a Cr(VI) species and thermal reoxidation of Cr(V) by CCl₃OOH produces radicals that initiate further decomposition.