ISSN:
0538-8066
Schlagwort(e):
Chemistry
;
Physical Chemistry
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
The kinetics and mechanism of the gas-phase reaction of Cl atoms with CH2CO have been studied with a FTIR spectrometer/smog chamber apparatus. Using relative rate methods the rate of reaction of Cl atoms with ketene was found to be independent of total pressure over the range 1-700 torr of air diluent with a rate constant of (2.7 ± 0.5) × 10-10 cm3 molecule-1 s-1 at 295 K. The reaction proceeds via an addition mechanism to give a chloroacetyl radical (CH2ClCO) which has a high degree of internal excitation and undergoes rapid unimolecular decomposition to give a CH2Cl radical and CO. Chloroacetyl radicals were also produced by the reaction of Cl atoms with CH2ClCHO; no decomposition was observed in this case. The rates of addition reactions are usually pressure dependent with the rate increasing with pressure reflecting increased collisional stabilization of the adduct. The absence of such behavior in the reaction of Cl atoms with CH2CO combined with the fact that the reaction rate is close to the gas kinetic limit is attributed to preferential decomposition of excited CH2ClCO radicals to CH2Cl radicals and CO as products as opposed to decomposition to reform the reactants. As part of this work ab initio quantum mechanical calculations (MP2/6-31G(d,p)) were used to derive ΔfH298(CH2ClCO) = -(5.4 ± 4.0) kcal mol-1. © 1996 John Wiley & Sons, Inc.
Zusätzliches Material:
4 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/kin.8
Permalink
