Kinetics and equilibria of the reaction between bromine and ethyl ether. The CH bond dissociation energy in ethyl ether

The kinetics and equilibria of the reaction:\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm Br} + {\rm CH}_{\rm 3} {\rm CH}_{\rm 2} {\rm OCH}_{\rm 2} {\rm CH}_{\rm 3} {\rm}\mathop {{\rm \rightleftharpoons}}\limits^{\rm 1} {\rm HBr} + {\rm CH}_{\rm 3} {\rm CHOCH}_{\rm 2} {\rm CH}_{\rm 3} $$\end{document}have been studied in the temperature range 298–333 K by using the very low pressure reactor (VLPR) technique. Combining the estimated entropy change of reaction (1), ΔS   ° 1= 8.1 ± 1.0 eu, with the measured ΔG   ° 1 , we find ΔH   ° 1= 4.2 ± 0.4 kcal/mol; ΔH   ° f (CH 3 CHOC 2 H 5 ) = −20.2 kcal/mol, and DH° [ Et OCH(Me)‐H] = 91.7 ± 0.4 kcal/mol. We find:\documentclass{article}\pagestyle{empty}\begin{document}$$ \log k_1 (1/{\rm mol s)} = 10.8(\pm 0.7) - (3.9 \pm 4.0)/\theta $$\end{document}where θ = 2.3 RT in kcal/mol. It has been shown that the reaction proceeds via a loose transition state and the “contact TS ” model calculation gives a very good agreement with the observed value.