ISSN:
0538-8066
Keywords:
Chemistry
;
Physical Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The photolysis of formamide vapor at 2062 Å has been studied in a flow system with results essentially similar to those obtained previously under static conditions and higher conversions. The rotating-sector technique has been applied to the radical-chain decomposition of formamide under conditions (305°C, 11.5 torr) such that decomposition of the carbamyl (NH2CO) radical was rate controlling, so that [NH2CO] ≫ [NH2]. A rate constant of (3.1 ± 1.0) × 1010(M·sec)-1 was obtained for bimolecular chain termination by carbamyl radicals. A concurrent first-order radical loss, probably at the surface, was taken into account by the treatment described by Shepp. Both oxamide and HNCO were tentatively identified as termination products, suggesting the occurrence of both combination and disproportionation,\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l} 2{\rm NH}_2 {\rm CO} \to {\rm NH}_{\rm 2} {\rm CO} \cdot {\rm CO} \cdot {\rm NH}_{\rm 2} \\ \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \to {\rm HNCO + NH}_{\rm 2} {\rm CHO} \\ \end{array} $$\end{document} but quantitative estimates of the relative rates were not possible. From the rate constant for chain termination, and relative rate constants obtained previously, Arrhenius parameters A∞ = (5.9 ± 2.0) × 1012 sec-1 and A0 = (1.04 ± 0.35) × 1014 (M·sec)-1 were estimated for the unimolecular decomposition of carbamyl radicals in the high and low pressure limits.
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/kin.550050104
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