ISSN:
0538-8066
Schlagwort(e):
Chemistry
;
Physical Chemistry
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
Absolute rate constants were determined for the gas phase reactions of OH radicals with a series of esters using the flash photolysis resonance fluorescence technique. Experiments were performed over the temperature range 240-440 K at total pressures (using Ar diluent gas) between 25-50 torr. The kinetic data for methyltrifluoroacetate (k1) over the complete temperature range, and for methylacetate (k2), and ethylacetate (k3) over the range 296-440 K were used to derive the Arrhenius expressions; \documentclass{article}\pagestyle{empty}\begin{document}$$k_1 = (3.0 \pm 0.7) \times 10^{- 13} {\rm \,exp[- (512} \pm {\rm 78)/}T]{\rm \,cm}^{\rm 3}\, {\rm \,molecule}^{{\rm - 1}}\, {\rm s}^{{\rm - 1}}$$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$k_2 = (8.3 \pm 3.5) \times 10^{- 13} {\rm \,exp[- (260} \pm 150{\rm)/}T]{\rm \,cm}^{\rm 3}\, {\rm \,molecule}^{{\rm - 1}}\, {\rm s}^{{\rm - 1}}$$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$k_3 = (2.3 \pm 0.2) \times 10^{- 12} {\rm \,exp[- (131} \pm 28{\rm)/}T]{\rm \,cm}^{\rm 3}\, {\rm \,molecule}^{{\rm - 1}}\, {\rm s}^{{\rm - 1}}$$\end{document} At 296 K, the measured rate constants (in units of 10-13 cm3 molecule-1 s-1) were: k1 = (0.52 ± 0.08), k2 = (3.41 ± 0.29), and k3 = (15.1 ± 1.4). Room temperature rate constants for the OH reactions with several other aliphatic esters were also measured. These were (in the above units): methylformate, (2.27 ± 0.34); ethylformate, (10.2 ± 1.4); n-propylformate, (23.8 ± 2.7); n-butylformate, (31.2 ± 3.3); n-propylacetate, (34.5 ± 3.4); i-propylacetate, (37.2 ± 2.9); n-butylacetate, (41.5 ± 3.0); s-butylacetate, (56.5 ± 5.9); methylpropionate, (10.3 ± 0.4); ethylpropionate, (21.4 ± 3.0); n-propylpropionate, (40.2 ± 3.2); methylbutyrate, (30.4 ± 3.3); ethylbutyrate, (49.4 ± 3.8); n-propylbutyrate, (74.1 ± 3.2), and n-butylbutyrate, (106 ± 13), error limits represent 2σ from linear least-squares analyses. The results are discussed in terms of the reaction mechanisms and are compared to previous literature data.
Zusätzliches Material:
4 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/kin.550200210
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