Kinetics of Cl Atom Reactions with C2H5Cl and C2H4Cl Radical and the Disproportionation of 2C2H4Cl at 298 K and at Millitorr Pressures

The bimolecular reaction Cl + C2H5Cl → HCl + C2H4Cl (1) is studied in the very-low-pressure reactor (VLPR) system at room temperature. Detailed mass spectrometric analysis of simultaneous reactant consumption and product formation rates indicates that the overall mechanism also includes two disproportionation reactions:  Cl + C2H4Cl → HCl + C2H3Cl (2) and 2C2H4Cl → C2H5Cl + C2H3Cl (3). Rate constants obtained for these reactions are:  k1 = (8.07 ± 0.36) × 10-12, k2 = (1.18 ± 0.06) × 10-11, and k3 = (1.83 ± 0.15) × 10-12 cm3/(molecule-s). The decrease in the reactivity of C2H5Cl compared with C2H6 reactivity in reaction type (1) correlates well with the electronegativity of the Cl substituent. The decrease points to a dipole−dipole repulsion in the transition state. Preliminary measurement of the reaction of C2H4Cl radical with Cl2 yields a value of k5 = (1.7 ± 1.0) × 10-13 cm3/(molecule-s).