KINETICS OF THE REACTION Cl+C2H4C2H3+HCl. HEAT OF FORMATION OF THE VINYL RADICAL

Article abstract of DOI:10.1021/j100320a050

The bimolecular rate constant for the title reaction has been measured by using the very low pressure reactor technique at 2631=(5.66+/-0.7)*1E-13 cm³/(molecule s) and from the range of temperature measurements log k₁(cm³/(molecule s))=-(10.50+/-0.2)-(2.8+/-0.4)/θ where θ=2.303RT (kcal/mol).In addition, the ratio k₁/k_-1 was also measured over this temperature range.The value of K₁ at room temperature was found to be 1.10+/-0.16.From the Van't Hoff plot of ln K₁ versus 1/T the values of heat of formation of the vinyl radical and C-H bond strength in ethylene are 66.7+/-0.5 and 106.3+/-0.4 kcal/mol, respectively.From more reliable third-law calculations at 293 K, ΔH_f^o(C2H3)=66.2+/-0.4 kcal/mol and DH^o(C2H3-H)=105.8+/-0.4 kcal/mol.Transition-state (TS) models of the reaction rule out a linear TS in favor a bent TS.The TS A factor was estimated to be 10^10.60L/(mol s), in fair agreement with the experimental value of 10^10.50L/(mol s).