Photochlorination of Chloroethane and Chloroethane-d5

Article abstract of DOI:10.1021/j150651a036

The hydrogen/deuterium abstraction from C2H5Cl and C2D5Cl by ground-state chlorine atoms has been investigated between 8 and 94 deg C.Results from the internal competition in chloroethane and chloroethane-d₅ combined with the results of external competition with CH4 as the reference reaction have yielded rate constant data for the following reactions: CH3CH2Cl + Cl -> CH3CHCl + HCl, k_2s; CH3CH2Cl + Cl -> CH2CH2Cl + HCl, k_2p; CD3CD2Cl + Cl -> CD3CDCl + DCl, k_2s,D; CD3CDCl + Cl -> CD2CD2Cl + DCl, k_2p,D.The temperature dependence of the rate constants (cm³s^-1) is given by k_2s = (1.43 +/- 0.29) X 1E-11 exp<-(462 +/- 71)/T>, k_2p = (1.35 +/- 0.28) X 1E-11 exp<-(871 +/- 72)/T>, k_2s,D = (0.72 +/- 0.14) X 1E-11 exp <-(468 +/- 70)/T>, and k_2p,D = (0.60 +/- 0.12) X 1E-11 exp<-(1156 +/- 72)/T>.The results confirm the general trend of chlorine atom attack being faster at the substituted carbon atom.Kinetic isotope effects for the abstraction of primary and secondary hydrogen are k_H/k_D = 5.8 and 2.0 at 298 K, respectively.The magnitude of these relatively weak isotope effects agrees with expectations based on other exothermic chlorination reactions and suggests that in the temperature range of the investigation tunneling does not play an important role.