Experimental and Theoretical Study of the Kinetics and Mechanism of the Reaction of Cl Atoms with CH3CHClCH3 and CD3CDClCD3.

The overall rate constants for H-abstraction (kH) from CH3CHClCH3 and D-abstraction (kD) from CD3CDClCD3 by chlorine atoms in the temperature range of 298-528.5 K were determined and are described by the expressions: kH = (3.52 ±0.21)×10-11 exp(-184 ±19/T) cm3molecule-1s-1 and kD = (1.91 ±0.16)×10-11 exp(-185 ±31/T) cm3molecule-1s-1 respectively. The results of the experiment show that the value of the kinetic isotope effect (kH/kD) for the overall rate constants is temperature independent and is equal to 1.85 ±0.17. A theoretical examination of these reaction mechanisms revealed some unusual properties, such as negative values of the activation energy for the H-abstraction reaction from the secondary carbon atom. Moreover, it was proved that in the radical process of H-abstraction from the primary carbon atom of 2-chloropropane the created R-Cl···Cl complex is the most stable structure responsible for the value of the activation energy of this transformation.