Detailed Kinetic Investigation of the C2H5+Cl2 Reaction and Analysis of the Reaction of CH3+Cl2 Initiated by H-Atom Contamination at 298K and at Millitorr Pressures

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Abstract
The bimolecular reaction: C2H5 + Cl24→ C2H5Cl + Cl is studied in the very low pressure reactor (VLPR) system at 298K starting with Cl/C2H6/Cl2 mixtures. Mass conservation is found to be 97 ± 3% for the overall chemical change in the system. From the C2H5Cl product formation kinetics, k4=(1.05±0.05)·10-12cm3/(molecule-s) is derived. Two independent estimates of the A factor gives A4=1.3 ·10-12cm3/(molecule-s). These parameters yield a positive activation energy of 0.13 kcal/mol in contrast with recently reported negative activation energy values. Some side reactions of small extent are initiated by H atom contamination in the system. The measurement of CH3Cl product formed from CH3+Cl211→CH3Cl+Cl gives k11=(3.4±0.3) · 10-12cm3/(molecule-s) with an estimated A factor of A11=5.0×10-12cm3/(molecules). The source of CH3 radicals is the side reaction H+C2H5→2CH3.