Steric Effects of Alkylmagnesium Chlorides in the Grignard Reaction with Silanes

Abstract

Rate constants for the reactions of methylvinyldichlorosilane and tetraethoxysilane with alkylmagnesium chlorides RMgCl (R = Et, n-Bu, i-Bu, i-Pr, s-Bu, t-Bu) in diethyl ether were determined. Excellent correlations of rate data with steric constants E_S(Si) by Cartledge and v′ by Charton were found for the reaction of methylvinyldichlorosilane. Linear correlations with break points were obtained for the tetraethoxysilane reaction. It was assumed that this could be referred to a change in the reaction mechanism.

Keywords:

• Grignard reaction
• kinetics
• Linear Free Energy (LFE) relationships
• silanes

Acknowledgments

This work was financially supported by the Dow Corning Corporation (Midland, USA), and the Estonian Science Foundation (grant No 6512).

Notes

^aA rough estimation from previous data. ¹⁹

^aTaft steric parameters revised by MacPhee et al. ³²

^bSteric parameters by Dubois corrected for hyperconjugation according Palm ³¹ (Eq. 3).

^cSteric parameters by Cartledge. ¹¹

^dSteric parameters by Charton. ³³

^eCalculated from our experimental data using Eq. (4).

^aFor specification, see footnotes to Table II.