Thermal rate constant for addition of chlorine atoms to ethylene

The relative reaction rate constant for removal of chlorine (Cl) atoms by addition to ethylene (C2H4) in the gas phase at 4000-torr pressure has been measured at 298 K by a competitive radiochemical technique to be 2.9 +- 0.1 times faster than the abstraction of H from ethane (C2H6) by Cl. This removal rate corresponds to an apparent reaction rate constant of (16.6 +- 1.8) x 10-11 cm3 molecule-1s-1, based on the measured value for reaction with C2H6. Correction for back-reaction of C2H4Cl* at 4000 torr leads to an estimated absolute reaction rate constant of (19 +- 2) x 10-11 cm3 molecule-1s-1 for k1, Cl + C2H4 → C2H4 → C2H4Cl* (1). The relative rates of abstraction by Cl of H from hydriodic acid (HI) and phosphine (PH3) are 2.21 +- 0.10 and 4.13 +- 0.13 times faster than abstraction from C2H6