Thermische Zerfallsreaktionen von Nitroverbindungen in Stosswellen. III: Dissoziation von 1-Nitropropan und 2-Nitropropan

The pyrolysis of 1- and 2-nitropropane highly diluted in Ar has been studied in shock waves at temperatures K 915 < T < 1200 K and total gas concentrations 7 · 10^?6 mol cm^?3 < Ar] < 1.5 · 10^?4 mol cm^?3. The reactions behind the shock waves have been followed by recording light absorption-time profiles of the decomposing molecules and the produced NO₂ Under the conditions of the experiments, the primary reaction step in both cases is the C? N bond:fission: \documentclass{article}\pagestyle{empty}\begin{document}$ \begin{array}{rcl} {\rm 1} - {\rm C}_{\rm 3} {\rm H}_{\rm 7} {\rm NO}_{\rm 2} {\rm (} + {\rm M)} &\to & n - {\rm C}_{\rm 3} {\rm H}_{\rm 7} + {\rm NO}_{\rm 2} {\rm (} + {\rm M)\quad k} = 2.3 \cdot 10^{15} {\rm exp }(- 55{\rm kcal mol}^{ - 1} /{\rm RT}){\rm s}^{ - 1} \\ 2 - {\rm C}_{\rm 3} {\rm H}_{\rm 7} {\rm NO}_{\rm 2} {\rm (} + {\rm M)} &\to & i - {\rm C}_{\rm 3} {\rm H}_{\rm 7} + {\rm NO}_{\rm 2} {\rm (} + {\rm M)\quad k} = 2.4 \cdot 10^{15} {\rm exp }(- 54{\rm kcal mol}^{ - 1} /{\rm RT}){\rm s}^{ - 1} \\ \end{array} $\end{document} (first order rate constants k measured at concentrations of Ar] ? 10^?4 mol cm^?3). At these concentrations the reactions are near to the high pressure limit. By varying the Ar-concentrations over one order of magnitude, only a slight pressure dependence was found. Reaction mechanisms which account for NO₂ removal are discussed.