CH3CO REACTIONS WITH CL-2 AND O-2 - MORE EVIDENCE FOR HCL ELIMINATION FROM THE CH3CHCLO RADICAL

The rate constant for the reaction of CH3CO with Cl-2 (k(1)) has been measured relative to that with O-2 (k(2)) using UV Irradiation of mixtures of CH3CHO, Cl-2, O-2, and N-2 to generate Cl atoms, which react with CH3CHO to form CH3CO. Consumption of CH3CHO and formation of CH3COCl were monitored by FTIR spectroscopy and used to determine k(1)/k(2) = 7.9 +/- 0.5 at 700 Torr and 296 K. The Cl-initiated oxidation of mixtures of C2H5Cl, Cl-2, O-2, and N-2 results in a monotonic increase in CH3COCl yield as the [Cl-2]/[O-2] ratio increases consistent with the presence of the CH3CO radical. A lower limit to k(1)/k(2) deduced from these experiments is 40% smaller than that measured above. These results support CH3CO as an intermediate in the oxidation process formed by molecular elimination of HCl from the CH3CHClO radical (CH3CHClO --> CH3CO + HCl). During these experiments the rate constant for reaction of CH3CHCl with Cl-2 (k(3)) relative to that with O-2 (k(4)) was also measured (k(3)/k(4) = 0.42 +/- 0.02).