Gasp-phase reactions of Cl atoms with propane, n-butane, and isobutane

Using the relative kinetic method, rate coefficients have been determined for the gas-phase reactions of chlorine atoms with propane, n-butane, and isobutane at total pressure of 100 Torr and the temperature range of 295-469 K. The Cl-2 photolysis (lambda = 420 nm) was used to generate Cl atoms in the presence of ethane as the reference compound. The experiments have been carried out using GC product analysis and the following rate constant expressions (in cm(3) molecule(-1) s(-1)) have been derived: (7.4 +/- 0.2) x 10(-11) exp \-(70 +/- 11)/T\, Cl + C3H8 --> HCl + CH3CH2CH2; (5.1 +/- 0.5) x 10(-11) exp\(104 +/- 32)/T\, Cl + C3H8 --> HCl + CH3CHCH3; (7.3 +/- 0.2) x 10(-11) exp\-(68 +/- 10)/T\, Cl + n-C4H10 --> HCl + CH3 CH2CH2CH2; (9.9 +/- 2.2) x 10(-11) exp\(106 +/- 75)/T\, Cl +n-C4H10 --> HCl + CH3CH2CHCH3; (13.0 +/- 1.8) x 10(-11) exp\-(104 +/- 50)/T\, Cl + i-C4H10 --> HCl +CH3CHCH3CH2; (2.9 +/- 05) x 10(-11) exp\(155 +/- 58)/T\, Cl + i-C4H10 --> HCl + CH3CCH3CH3 (all error bars are +/-2sigma precision). These studies provide a set of reaction rate constants allowing to determine the contribution of competing hydrogen abstractions from primary, secondary, or tertiary carbon atom in alkane molecule. (C) 2002 Wiley Periodicals, Inc.