The kinetics and mechanisms of chlorine atom reactions with alkylbenzenes and alkylnaphthalenes.

摘要

The relative rate method was used to study the kinetics and mechanism of Cl atom reactions with a series of alkylbenzenes and alkylnaphthalenes at 298 K and 1 atm. The following rate constants for the alkylbenzenes were obtained (in units of 10-10 cm3molecule -1s-1 with uncertainties of +/-2sigma): ethylbenzene, 1.1 +/- 0.2; n-propylbenzene, 1.9 +/- 0.3; butylbenzene, 2.6 +/- 0.6; o-xylene, 1.5 +/- 0.2; m-xylene, 1.3 +/- 0.1; p-xylene, 1.5 +/- 0.2; 1,3,5-trimethylbenzene, 2.2 +/- 0.4; 1,2,3-trimethylbenzene, 2.5 +/- 0.3; 1,2,4-trimethylbenzene, 2.5 +/- 0.2. The kinetic isotope effect (KIE) measurements and product analyses suggest that the reaction between Cl atoms and alkylbenzenes proceeds via initial hydrogen atom abstraction from the alkyl substituent(s). Preliminary results obtained for the rate constant of the Cl atom reaction with 1-methylnaphthalene (1-MN) in a 21 L reaction cell, (1.3 +/- 0.4) x 10-10 cm3molecule -1s-1, are in excellent agreement with the literature value. The results using a smaller reaction cell varied with initial reactant and reference concentration and were also dependent on the bath gas used. KIE measurements and product analyses of the Cl atom reaction with 1-MN suggest that the mechanism proceeds via abstraction from the methyl group. Implications for fundamental and environmental chemistry will be discussed.