ISSN:
0538-8066
Keywords:
Chemistry
;
Physical Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The overall reaction (1) \documentclass{article}\pagestyle{empty}\begin{document}$$ Br_2 + CH_3 I \to IBr + CH_3 Br $$\end{document} occurs readily in the gas phase, even at room temperature in the dark. The reaction is much faster than the corresponding process \documentclass{article}\pagestyle{empty}\begin{document}$$ Br_2 + CF_3 I \to IBr + CF_3 Br $$\end{document} and does not involve the normal bromination mechanism for gas phase reactions. Reaction (1) is probably heterogeneous although other mechanisms cannot be excluded.The overall reactions (1) \documentclass{article}\pagestyle{empty}\begin{document}$$ Br_2 + CH_3 I \to IBr + CH_3 Br $$\end{document} (2) \documentclass{article}\pagestyle{empty}\begin{document}$$ Br_2 + 2CH_3 I \to I_2 + 2CH_3 Br $$\end{document} proceed, for all practical purposes, completely to the right-hand side in the vapor phase. The expected mechanism is (3) \documentclass{article}\pagestyle{empty}\begin{document}$$ Br_2 \to 2Br $$\end{document} (4) \documentclass{article}\pagestyle{empty}\begin{document}$$ Br + CH_3 I \to IBr + CH_3 $$\end{document} (5) \documentclass{article}\pagestyle{empty}\begin{document}$$ CH_3 + Br_2 \to CH_3 Br +Br $$\end{document} (6) \documentclass{article}\pagestyle{empty}\begin{document}$$ Br + IBr \to Br_2 +I $$\end{document} (7) \documentclass{article}\pagestyle{empty}\begin{document}$$ I + I + M \to I_2 + M $$\end{document} where reaction (3) is initiated thermally or photochemically. Reaction (4) is of interest because little kinetic data are available on reactions involving abstraction of halogen by halogen and also because an accurate determination of the activation energy E4 would prmit us to calculate an acccurate value of the bond dissociation energy D(CH3—I).
Additional Material:
1 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/kin.550050613
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