1252913-92-0Relevant articles and documents
The β-silicon effect. 4: Substituent effects on the solvolysis of 1-alkyl-2-(aryldimethylsilyl)ethyl trifluoroacetates
Fujiyama, Ryoji,Alam, Md. Ashadul,Shiiyama, Aiko,Munechika, Toshihiro,Fujio, Mizue,Tsuno, Yuho
, p. 819 - 827 (2011/04/24)
Solvolysis rates of 2-(aryldimethylsilyl)-1-methylethyl and 2-(aryldimethylsilyl)-1-tert-butylethyl trifluoroacetates were determined conductimetrically in 60% (v/v) aqueous ethanol. The effects of aryl substituents at the silicon atom on the solvolysis rates at 50 °C were correlated with σmacr; parameters of r+ = 0.15 with the Yukawa-Tsuno equation, giving ρ values of-1.5 for both secondary α-Me and α-tert-Bu systems. The ρ values for those secondary systems are less negative than-1.75 for the 2-(aryldimethylsilyl)ethyl system that proceeds by the Eaborn (non-vertical) mechanism, while they are distinctly more negative than-0.99 for 2-(aryldimethylsilyl)-1-phenylethyl system that should proceed by the Lambert (vertical) mechanism. There was a fairly linear relationship between the reaction constants (ρ) for the β-silyl substituent effects and the solvolysis reactivities for a series of β-silyl substrates. The solvolyses of the α-Me and tert-Bu substrates proceed through the transition state (TS) with an appreciable degree of the β-silyl participation, close to the Eaborn (non-vertical) TS rather than to the Lambert (vertical) TS. Copyright
