ISSN:
0538-8068
Schlagwort(e):
Chemistry
;
Physics Chemistry
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
The kinetics of the nitric oxide catalyzed, homogeneous, gas-phase isomerization of 1,trans-3,trans-5-heptatriene have been studied for temperatures ranging between 130°C and 241°C. The very clean reaction involves exclusive geometrical isomerization about the 5,6-π-bond. The observed rate constants for \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm NO} + trans - {\rm 3,}trans{\rm - 5}\stackrel{1}{\rightarrow}trans - 3,cis - 5 + {\rm NO} $\end{document} can be represented (with standard errors) by log k1 = (7.18 ± 0.06) - (16.75 ± 0.12)/θ, where θ = 2.303 RT in kcal/mole. The consecutive-step reaction mechanism involves addition of NO to the double bond (Ka, b = ka/kb), followed by rotation of the 5,6-C—C bond in the adduct radical (kc.)Analysis of the observed activation parameters shows, that kc is rate-controlling and consequently k1 = kcKa, b. Estimates of kc and Ka, b lead to a value of k1 in good agreement with experiment.Comparing our data with those previously obtained for the similar 1,3-pentadiene system results in a value for the extra stabilization energy generated in the 1,3-heptadienyl radical of 18.5 ± 1.7 kcal/mole. This value is discussed in view of comparable data in the literature.
Zusätzliches Material:
1 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/kin.550020403
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