Chlorination Chemistry. 2. Rate Coefficients, Reaction Mechanism, and Spectrum of the Chlorine Adduct of Allene

Abstract

Cavity ring-down (CRD) spectroscopy and ab initio calculations have determined the reaction rate coefficients, mechanism, and thermochemistry relevant to the addition of a chlorine atom to allene. Chlorine atoms were produced by laser photolysis at 351 nm and the addition reaction products were probed at a variable delay by CRD spectroscopy using a second laser pulse. Ab initio results indicate that the only persistent addition product is the 2-chloroallyl (C 3 H 4 Cl) radical. We measured the continuum spectrum of the 2-chloroallyl radical between 238 and 252 nm and determined the absorption cross section, σ 240 (C 3 H 4 Cl) ) (2.5 ( 0.5) × 10 -17 cm 2 . By fitting the C 3 H 4 Cl absorption data to complex kinetic mechanisms, rate coefficients at 298 K were found to be k(Cl+C 3 H 4 ; 656 Pa, N 2 ) ) (1.61 ( 0.27) × 10 -10 cm 3 molecule -1 s -1 , k(Cl+C 3 H 4 ; 670 Pa, He) ) (1.34 ( 0.24) × 10 -10 cm 3 molecule -1 s -1 , and k(Cl+C 3 H 4 ; 1330 Pa, He) ) (1.75 ( 0. 25) × 10 -10 cm 3 molecule -1 s -1 . The rate coefficient of the self-reaction displayed no pressure dependence between 434 and 1347 Pa in N 2 buffer giving k(C 3 H 4 Cl+C 3 H 4 Cl) ) (3.7 ( 1.0) × 10 -11 cm 3 molecule -1 s -1 . A study of the addition reaction of 2-chloroallyl radical and oxygen molecule determined σ 240 (C 3 H 4 ClO 2 ) ) (3.6 ( 0.7) × 10 -18 cm 2 and k(O 2 +C 3 H 4 Cl, 705 Pa N 2 ) ) (3.6 ( 0.4) × 10 -13 cm 3 molecule -1 s -1 . The listed uncertainties denote two standard deviations, and those for rate coefficients include the uncertainty of the appropriate absorption cross section.

Kinetics and Thermochemistry of the Reaction of 2-Chloroallyl Radicals with Molecular Oxygen

“…The results of the current study and those of ref 18 are not sufficient to allow a reliable extrapolation of the rate constant to the high-pressure limit. However, it seems plausible that the high-pressure limit rate constant of reaction 3 at room temperature can be similar to that of the allyl + O 2 reaction, (6 ( 2) × 10 -13 cm 3 molecule -1 s -1 , obtained in the experiments of Jenkin et al 37 at the pressure of 760 Torr of synthetic air.…”

“…The only experimental information on the kinetics of CH 2 -CClCH 2 existing in the literature is the room-temperature rate constants of reaction 3 and that of recombination of 2-chloroallyl radicals reported by Atkinson and Hudgens. 18 These authors generated 2-chloroallyl radicals in the reaction of Cl with allene and studied their kinetics using cavity ring-down spectroscopy. The rate constant of reaction 3 obtained at 298 K and 5.3 Torr ln(K P /bar -1 ) ) -∆G°T/RT…”

Kinetics and products of propargyl (C3H3) radical self-reactions and propargyl-methyl cross-combination reactions

“…In a recent work by Atkinson and Hudgen [23] Table II. These findings indicate that the inclusion of the preceding secondary reactions results in yields of the major products that are only slightly lower than those derived from using Mechanism I. On average, the yields of C 2 H 6 , C 4 H 6 , and C 6 H 6 were reduced by less than 4%, 3%, and 1.5%, respectively, which are all within the range of our measurement uncertainties (5 -10%).…”

Kinetics of reactions of chlorine atoms with a series of alkenes at 1 atm and 298 K: structure and reactivity

“…The kinetics of the chlorine atom reactions under various conditions of temperature and pressure with simple alkenes such as ethene, propene, 1-butene, trans-2-butene, and 1-pentene 17,21,22, and with some dienes [50][51][52][53][54][55][56][57][58][59][60] have been reported. The reaction proceeds primarily by reversible addition to the double bond; at sufficiently high pressures, the chlorine-alkene adduct is stabilized as a chlorinated alkyl radical, for example in the case of propene:…”