| Autor: |
Tuulmets A; Institute of Organic and Bioorganic Chemistry, University of Tartu, Tartu 51014, Estonia. tuulmets@chem.ut.ee, Nguyen BT, Panov D, Sassian M, Järv J |
| Jazyk: |
angličtina |
| Zdroj: |
The Journal of organic chemistry [J Org Chem] 2003 Dec 26; Vol. 68 (26), pp. 9933-7. |
| DOI: |
10.1021/jo034941g |
| Abstrakt: |
Kinetics of the reactions of butylmagnesium chloride and phenylmagnesium bromide with tetraethoxysilane and methyltrichlorosilane was investigated in diethyl ether and diethyl ether-toluene mixtures. Replacement of ether by toluene significantly accelerates the reaction with alkoxysilanes, while no effect was found for the reaction with chlorosilanes. We established that the reaction with alkoxysilanes consists of replacement of a donor molecule at the magnesium center by the silane followed by subsequent rearrangement of the complex to products through a four-center transition state. Chlorosilanes react differently without solvent molecule replacement but also via a four-center transition state. Large negative activation entropies are consistent with formation of cyclic transition states. Small activation enthalpy values together with remarkable exothermicity point to early transition states of the reactions. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
|
