ISSN:
0538-8066
Keywords:
Chemistry
;
Physical Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The kinetics of the gas-phase reaction of 2,2,2-trifluoroethyl iodide with hydrogen iodide has been studied over the temperature range of 525°K to 602°K and a tenfold variation in the ratio of CF3CH2I/HI. The experimental results are in good agreement with the expected free radical-mechanism: \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm I}_2 + {\rm M} \rightleftharpoons 2{\rm I} + {\rm M} $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm RI} + {\rm I}\mathop{\rightleftharpoons}\limits_2^1 {\rm R} + {\rm I}_2 $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm R} + {\rm HI} \mathop{\rightleftharpoons} \limits_{4}^{3} {\rm RH} + {\rm I} $$\end{document}An analysis of the kinetic data yield:\documentclass{article}\pagestyle{empty}\begin{document}$$ \log (k_1/ \rm I. \rm mol^{ - 1} s^{ - 1}) = (11.5 \pm 0.1) - (1.99 \pm 0.2)/\theta $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ \log k_2 /k_3 = (0.65 \pm 0.4) + 1.0/\theta $$\end{document} where θ =2.303RT in kcal/mol. If these results are combined with the assumption that E2 = 0 ± 1 kcal/mol, then one obtains DH0298 (CF3CH2—I) = 56.3 kcal/mol. This result may be compared with DH0298(CH3CH2—I) = 52.9 kcal/mol and suggests that substitution of three fluorines for hydrogen in the beta position strengthens the C—I bond slightly.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/kin.550050609
