Reactions of chromium atoms with chloromethanes

Article abstract of DOI:10.1007/BF02756059

The rate constants of the gas-phase reactions of the chromium atom with CCl₄, CHCl₃, and CH₂Cl₂ were measured behind shock waves at 800-1400 K. The rate constants of hexacarbonyl decomposition and chromium atom yield agreed well. The rate of formation of chromium atoms was slightly lower than the rate of consumption of parent molecules. At > 800 K (lower-temperature boundary of the reactions of chromium atoms with chloromethanes), the yield of chromium atoms in the course of Cr(CO)₆ thermal decomposition may be considered an instantaneous process, i.e., its characteristic time is much shorter than the characteristic resolution time of the optical system. The rate constants were determined via monitoring a decrease in the chromium atom concentration with time. The available thermochemical data on the detachment of the chlorine atom from studied chloromethanes and on the dissociation of CrCl molecules showed that the reactions with the participation of CCl₄ and CHCl₃ were probably exothermic. A more detailed theoretical treatment of the reactions studied was complicated by the absence of accurate thermochemical data, primarily for the dissociation energy of the Cr-Cl bond.