title: Mechanisms for the breakdown of halomethanes through reactions with ground-state cyano radicals.
abstract: One route to break down halomethanes is through reactions with radical species. The capability of the artificial force-induced reaction algorithm to efficiently explore a large number of radical reaction pathways has been illustrated for reactions between haloalkanes (CX3 Y; X=H, F; Y=Cl, Br) and ground-state ((2) Σ(+) ) cyano radicals (CN). For CH3 Cl+CN, 71 stationary points in eight different pathways have been located and, in agreement with experiment, the highest rate constant (10(8) s(-1)  M(-1) at 298 K) is obtained for hydrogen abstraction. For CH3 Br, the rate constants for hydrogen and halogen abstraction are similar (10(9) s(-1)  M(-1) ), whereas replacing hydrogen with fluorine eliminates the hydrogen-abstraction route and decreases the rate constants for halogen abstraction by 2-3 orders of magnitude. The detailed mapping of stationary points allows accurate calculations of product distributions, and the encouraging rate constants should motivate future studies with other radicals.
authors.affiliation: Department of Chemistry-Ångström Laboratory, Uppsala University, Box 518, 751 20, Uppsala (Sweden).
authors.forename: Pooria
authors.initials: P
authors.lastname: Farahani
authors.forename: Satoshi
authors.initials: S
authors.lastname: Maeda
authors.forename: Joseph S
authors.initials: JS
authors.lastname: Francisco
authors.forename: Marcus
authors.initials: M
authors.lastname: Lundberg
keywords: gas-phase reactions; quantum chemistry; radical reactions; reaction mechanisms; transition states