PRESSURE-DEPENDENCE OF THE REACTION CL+C2H2 OVER THE TEMPERATURE-RANGE 230-K TO 370-K

The pressure dependence of reaction (1), Cl + C2H2 + M --> C2H2Cl + M, has been measured by a relative rate technique using the pressure independent abstraction reaction (2), Cl + C2H6 --> C2H5 + HCl, as the reference. Values of k1/k2 were measured at pressures between 25 and 1300 torr at four temperatures ranging from 252 to 370 K, using air, N2, or SF6 diluent gases. Low pressure measurements (10-50 torr) were performed at 230 K. Assuming a temperature-independent center broadening factor of 0.6 in the Troe formalism and using the established value Of k2, these data can be used to determine the temperature dependent high and low pressure limiting rate constants over the range of conditions studied in air for reaction (1): k(infinity)(1) = 2.13 x 10(-10) (T/300)-1.045 cm3/molecule-s; and k0(1) = 5-4 x 10(-30) (T/300)-2.09 cm6/molecule2-s. molecule2-s. Use of these expressions yields rate constants with an estimated 20% accuracy including uncertainty in the reference reaction. The data indicate that the rate constant for a typical stratospheric condition at 30 km altitude is approximately 50% of that previously estimated.