Pyrolysis of 4,4‐bisperfluoromethylbutene‐1,4 01 in the gas phase

Pyrolysis of (CF 3 ) 2 C(OH)CH 2 CH=CH 2 , the reverse of the reaction between perfluoroacetone and propene, has been studied in the gas phase between 475° and 598°K. Even at 573°K, the unimolecular reaction rate constant appears to be in its pressure‐independent region at 20.0 torr pressure. In a quartz vessel, the decomposition is homogeneous. The specific unimolecular rate constant is\documentclass{article}\pagestyle{empty}\begin{document}$$k = T^{1/2} 10[^{(10.3 \pm 0.10) - (\frac{{40300 \pm 300}}{{4.575T}})}]\sec ^{ - 1}$$\end{document} where the limits are for one standard deviation. Combining these results with the previously reported results on the reverse reaction, the equilibrium constant for the reaction\documentclass{article}\pagestyle{empty}\begin{document}$${\rm C}_{\rm 3} {\rm H}_{\rm 6} + {\rm CF}_{\rm 3} {\rm COCF}_{\rm 3} {\rm \rightleftharpoons(CF}_{\rm 3} {\rm)}_{\rm 2} {\rm C(OH)CH}_{\rm 2} {\rm CH = CH}_{\rm 2}$$\end{document} is\documentclass{article}\pagestyle{empty}\begin{document}$$k_p = 10[^{(1/4.575)(-34.0 \pm 1.0) + (\frac{{18700 \pm 400}}{T})}]atm^{ - 1}$$\end{document} It is noteworthy that in the temperature range of the study of the forward reaction (448° to 573°K), the percentage of back reaction in the times of the experiments varies from less than 0.1 to 1.5. Using group additivities and the above Δ H 0 , Δ H   f 0of (CF 3 ) 2 CO is calculated to be −325.2 kcal/mole at 600°K and the average CC bond is 42.0 kcal/mole.