Experimental and Theoretical Study of the Kinetics and Mechanism of the Reaction of Chlorine Atoms with CH3CHCICH3 and CD3CDCICD3

The overall rate constants for H-abstraction (k(H)) from CH3CHCICH3 and D-abstraction (k(D)) from CD3CDCICD3 by chlorine atoms in the temperature range 298-528.5 K were determined and are described by the expressions: k(H) = (3.52 +/- 0.21) X 10(-11) exp(-184 +/- 19/T) cm(3) molecule(-1) s(-1) and k(D) = (1.91 +/- 0.16) X 10(-11) exp(-185 +/- 31/T) cm(3) molecule(-1) s(-1) respectively. The results of the experiment show that the value of the kinetic isotope effect (k(H)/k(D)) 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 center dot center dot center dot Cl complex is the most stable structure responsible for the value of the activation energy of this transformation.