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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.

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Abstract:© Versita Sp. z o.o. Keywords: Correlation analysis • Linear free energy relationships • Silicon compounds • Substituent effectsAvailable quantitative data of the reactivity of organosilicon compounds were subjected to correlation analysis. As an alternative to the carbon chemistry values, the scale of steric constants E S (Si) can be used for organosilicon compounds and the inductive effect is best expressed by two terms, involving the parameter of electronegativity of substituents. Alkyl substituents contribute to the reactivity exclusively through their steric effects, steric and polar effects in silicon compounds are additive and the resonance effect is insignificant. The correlation analysis can be employed in investigations of organosilicon reactions along with other methods.

Reactivity data for a number of reactions taking place at Si atoms in organosilicon compounds containing a variety of alkyl groups have been examined for statistical correlations with steric parameters. Four practically equivalent sets of parameters are now available for quantitative description of steric effects of alkyl substituents in organosilicon compounds. Alkyl substituents contribute to the reactivity exclusively with their steric effects. Steric effects in silicon compounds are additive.

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