ZIB

101

Digitale Medien

Recombination of carbon monoxide and oxygen atoms (1978)

Hardy, J. E. ; Gardiner, W. C. ; Burcat, A.

New York, NY : Wiley-Blackwell

International Journal of Chemical Kinetics 10 (1978), S. 503-517

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ISSN: 0538-8066

Schlagwort(e): Chemistry ; Physical Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The recombination of carbon monoxide and oxygen atoms was studied in reflected shock waves in H2:O2:CO:Ar = 0.1:1:24:75 with 1300 〈 T5 2200 K and 2 〈 P5 〈 4 atm. Reaction progress was monitored by observations of the carbon monoxide flame spectrum near 435 nm and carbon dioxide thermal emission near 4.2 μm. Data analysis was accomplished with the aid of computer modeling using a 27-reaction mechanism. Computer modeling experiments also showed that these measurements were sensitive primarily to the rate of the reaction CO + O + M = CO2 + M and only slightly sensitive to the rates of other reactions. The best fit to the data was achieved with a rate constant for this reaction of 7.7 × 10-35 exp[19 kJ/RT] cm6 s for the temperature range of these experiments. Correlation of this result and previous data covering the temperature range 250 〈 T 〈 11,000 K confirms that this recombination reaction is governed by a nonadiabatic curve crossing with an activation barrier of about 20 kJ and subsequent deactivation of a singlet CO2 molecule.

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/kin.550100508

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102

Digitale Medien

Masthead (1978)

New York, NY : Wiley-Blackwell

International Journal of Chemical Kinetics 10 (1978)

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ISSN: 0538-8066

Schlagwort(e): Chemistry ; Physical Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/kin.550100601

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103

Digitale Medien

The mechanism of the photochemical reactions of SO2 with isobutane excited at 3130 Å (1978)

Su, Fu ; Calvert, Jack G.

New York, NY : Wiley-Blackwell

International Journal of Chemical Kinetics 10 (1978), S. 557-580

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ISSN: 0538-8066

Schlagwort(e): Chemistry ; Physical Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The mechanism of the reactions of electronically excited SO2 with isobutane has been studied through the measurement of the initial quantum yields of product formation in 3130 Å irradiated gaseous binary mixtures of SO2 and isobutane and ternary mixtures of SO2, isobutane, C6H6 or CO2. Under low-pressure conditions (P 〈 10 torr) the kinetic treatment of the present data shows that only one singlet and one triplet state, presumably the 1B1 and 3B1 states, are involved in the photoreaction mechanism. The data give k2a = 8.4 × 109; SO2(1B1) + isobutane → products (2a); k5a ≃ k5 = 8.7 × 108 l./mol·sec; SO2(3B1) + isobutane → products (5a) SO2(3B1) + isobutane → (SO2) + isobutane (5b) k1a/k1 = 0.145 ± 0.037; SO2(1B1) + SO2 → SO2(3B1) + SO2 (1a) SO2(1B1) + SO2 → (2SO2) (1b) k2b/k2 = 0.273 ± 0.018; SO2(1B1) + isobutane → SO2(3B1) + isobutane (2b); SO2(1B1) + isobutane → (SO2) + isobutane (2c) error limits are ± 2 σ. The contribution from the excited SO2(1B1) molecules to the quantum yields of the photolyses of SO2-isobutane mixtures is not negligible. Under high-pressure conditions (P 〉 10 torr) the low-pressure mechanism coupled with the saturation effect on the phosphorescence lifetimes of SO2(3B1) molecules cannot alone rationalize the quantum yields. The evaluation suggests that some nonradiative intermediate state (X) is involved in the formation of “extra” triplet molecules. This ill-defined state decays largely nonradiatively to SO2 in experiments at low pressures, X → SO2 (12). In the presence of C6H6 the low-pressure data give k7 = (8.5 ± 1.8) × 1010, and the high-pressure data give k7 = (8.3 ± 0.6) × 1010 and (9.9 ± 0.9) × 1010l./mol·sec; SO2(3B1) + C6H6 → nonradiative products (7). These estimates are in good agreement with values directly measured from low-pressure lifetime studies, (8.1 ± 0.7) × 1010 and (8.8 ± 0.8) × 1010l./mol·sec.

Zusätzliches Material: 13 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/kin.550100604

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104

Digitale Medien

On the reactivity of diethyl hydroxyl amine toward free radicals (1978)

Abuin, E. ; Encina, M. V. ; Diaz, S. ; [weitere]

New York, NY : Wiley-Blackwell

International Journal of Chemical Kinetics 10 (1978), S. 677-686

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ISSN: 0538-8066

Schlagwort(e): Chemistry ; Physical Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Diethyl hydroxyl amine is an efficient trap for alkyl, alkoxy, and peroxy radicals. The specific rate constant for the reaction of ethyl radicals (gas phase, 25°C), tert-butoxy radicals (benzene solution, 115°C), and poly (peroxystyryl) peroxy radicals (styrene solution, 50°C) were evaluated as 7.2 × 105, 7.7 × 107, and 2.9 × 105 M-1·sec-1, respectively. Several possible secondary reactions of the nitroxide radicals are discussed.

Zusätzliches Material: 4 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/kin.550100704

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105

Digitale Medien

Kinetics and mechanism of hydrogen-oxygen difluoride reaction in magnesium (1978)

Houser, Thomas J.

New York, NY : Wiley-Blackwell

International Journal of Chemical Kinetics 10 (1978), S. 773-781

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ISSN: 0538-8066

Schlagwort(e): Chemistry ; Physical Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The kinetics of the H2-OF2 reaction was studied in the temperature range of 160°-310°C at 1 atm total pressure in a magnesium stirred-flow reactor. Initial concentration ranges were 1/2-1/2 mol·% OF2, 3/16-5 mol·% H2, and 1/4-5.0 mol·% O2; helium was used as the diluent. When the reactants were in a mole ratio of 3/2 (H2/OF2), the rate of disappearance of H2 was 1.5 times that of OF2, consistent with the previously reported stoichiometry. The rate of disappearance of OF2 was strongly influenced by OF2 concentration, weakly influenced by H2 concentration, and inhibited by the oxygen formed in the reaction. An increase in the surface area did not produce a significant change in the rate of reaction. These concentration dependencies led to a proposed ten-step mechanism from which was derived the following rate equation: \documentclass{article}\pagestyle{empty}\begin{document}$$ \frac{{- d(\rm {OF}_2)}}{{dt}} = \frac{{k_0 (\rm {OF}_2)^2}}{{(\rm {O}_2)^{1/2}}}\left(1 + \frac{{\alpha (\rm {OF}_2)}}{{\alpha (\rm {OF}_2) + \beta (\rm {H}_2)}}\right) $$\end{document} where k0 is a complex combination of elementary rate constants and α and β are elementary rate constants. An Arrhenius treatment of k0 gave \documentclass{article}\pagestyle{empty}\begin{document}$$ k_0 = 10^{8.41 \pm 0.24} \exp (- 17,300 \pm 500/RT)(\rm {l}./\rm {mol})^{1/2} /\sec $$\end{document}These experimental Arrhenius parameters are lower than those predicted from reported and estimated elementary rate constants. The possibility of heterogeneous contributions is discussed.

Zusätzliches Material: 1 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/kin.550100710

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