Thermal Decomposition of Some Alkyl Halides by a Shock-Tube Method

Abstract

The decomposition of several alkyl halides have been studied by a comparative rate method using a single‐pulse shock tube. Rate constants for the elimination of hydrogen halide from the parent molecule are compared with the rate of elimination of hydrogen bromide from isopropyl bromide. The Arrhenius expression for the latter reaction has previously been found to be $\mathrm{k(i}\mathrm{-}{\mathrm{C}}_3{\mathrm{H}}_7\mathrm{Br}{\text{)=10}}^{\text{13.62}}\exp \text{(−47 800/RT)}{\sec }^{\text{−1}}$ . On this basis, the following rate expressions have been obtained: $$\begin{array}{cc}\mathrm{\hspace{0.17em}k(}{\mathrm{C}}_2{\mathrm{H}}_5\mathrm{Br}{\text{)10}}^{\text{13.19}}\exp \text{(−53 700/RT)\hspace{0.17em}(}{\sec }^{\text{−1}})& {740}^{\circ }{\text{−940}}^{\circ }\mathrm{K},\\ \mathrm{\hspace{0.17em}k(}{\mathrm{C}}_2{\mathrm{H}}_5\mathrm{Cl}{\text{)=10}}^{\text{13.16}}\exp \text{(−56 460/RT)\hspace{0.17em}(}{\sec }^{\text{−1}})& {820}^{\circ }{\text{−1000}}^{\circ }\mathrm{K},\\ \mathrm{k(i}{\mathrm{-C}}_3{\mathrm{H}}_7\mathrm{Cl}{\text{)=10}}^{\text{13.64}}\exp \text{(−51 100)/RT)\hspace{0.17em}(}{\sec }^{\text{−1}})& {750}^{\circ }{\text{−950}}^{\circ }\mathrm{K},\\ \mathrm{\hspace{0.17em}k(i}{\mathrm{-C}}_3{\mathrm{H}}_7\mathrm{I}{\text{)=10}}^{\text{13.67}}\exp \text{(−45 065/RT)\hspace{0.17em}(}{\sec }^{\text{−1}})& {680}^{\circ }{\text{−850}}^{\circ }\mathrm{K},\\ \mathrm{\hspace{0.17em}k(t}{\mathrm{-C}}_4{\mathrm{H}}_9\mathrm{I}{\text{)=10}}^{\text{13.73}}\exp \text{(−38 080/RT)\hspace{0.17em}(}{\sec }^{\text{−1}})& {650}^{\circ }{\text{−760}}^{\circ }\mathrm{K}.\end{array}$$ These results are compared with the results of earlier low‐temperature studies. The advantages and reliability of this type of kinetic study are discussed.