The β-Silicon Effect. II. Substituent Effects on the Solvolysis of 1-Aryl-2-(aryldimethylsilyl)ethyl 3,5-Dinitrobenzoates
作者:Mizue Fujio、Yuzo Umezaki、Md. Ashadul Alam、Kiyoshi Kikukawa、Ryoji Fujiyama、Yuho Tsuno
DOI:10.1246/bcsj.79.1091
日期:2006.7
Solvolysis rates of 2-(dimethylphenylsilyl)-l-(Y-phenyl)ethyl 3,5-dinitrobenzoates were determined conductimetrically in 60% (v/v) aqueous ethanol. In order to clarify the nature of the β-Si participation quantitatively, the effects of α-aryl substituents on the rates were analyzed by means of the Yukawa-Tsuno Eq. The α-aryl (Y)-substituent effect at 25 °C was correlated with r ≅ 1.0 and p = -3.0,
2-(二甲基苯基甲硅烷基)-1-(Y-苯基)乙基 3,5-二硝基苯甲酸酯的溶剂分解速率在 60% (v/v) 乙醇水溶液中通过电导测定。为了定量阐明β-Si参与的性质,通过Yukawa-Tsuno方程分析了α-芳基取代基对速率的影响。25 °C 下的 α-芳基 (Y)-取代基效应与 r ≅ 1.0 和 p = -3.0 相关,与非甲硅烷基化 1-芳乙基系统的 -5.45 相比,该效应显着降低。甲硅烷基化和非甲硅烷基化底物的 log k Y /k H 之间存在线性关系:log(k Y /k H ) Si = 0.52 log(k Y /k H ) non-Si。这与扩展的 Bronsted 关系形式相同。Bronsted 系数 a = 0.52 似乎与相邻的甲硅烷基参与甲硅烷基桥接过渡态一致。