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Kinetic study of the bromine‐catalyzed alcoholysis of butoxytriethylsilane: n ‐Butoxy group– s ‐butoxy group exchange reaction
Author(s) -
Ito Katsuko,
Ibaraki Takeshi
Publication year - 1990
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550220308
Subject(s) - chemistry , bromine , catalysis , reaction rate constant , iodine , medicinal chemistry , reaction rate , kinetic energy , reaction mechanism , order of reaction , kinetics , organic chemistry , physics , quantum mechanics
In order to compare the catalytic activity of bromine with those of iodine and iodine monohalides, kinetic studies on the reaction, Et 3 SiOBu n + Bu s OH ⇌ Et 3 SiOBu s + Bu n OH, were undertaken. Pseudo first‐order rate constants were determined at 0°, 10°, 15°, 20°, and 30°C by means of gas chromatography on the reaction mixtures containing both butanols in excess. From the observed rate constants, the catalytic coefficients of bromine were evaluated as follows:\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l} k_{2_{{\rm Br}_{\rm 2}}} = 6.6 \times 10^7 {\rm exp}(- 44.5 \times 10^3 /RT); \\ k_{ - 2_{{\rm Br}_{\rm 2}}} = 8.1 \times 10^7 {\rm exp}(- 43.0 \times 10^3 /RT). \\ \end{array} $$\end{document}The enthalpies and entropies of activation were estimated to be (42.0 – 42.2) kJ/mol, −(103 – 104) J/K (forward reaction), and (40.4 − 40.7) kJ/mol, − (101 − 102) J/K (reverse reactions). These data suggest that bromine is much more active than iodine and iodine monohalides, and its high activity was interpreted on the basis of the structure of the reaction intermediate.