Acid catalyzed elimination of silanol from the cyclic cis-α,β-dihydroxysilanes 3–8 to cycloalkanones was studied at three different temperatures (298, 313 and 328 K). Silyldiols 3–7 hydrolyzed smoothly, while 8 was resistant to hydrolysis. The observed ease of elimination (reflected in the rate constants) was found to be related to the conformational flexibility of the ring and intramolecular hydrogen bonding. The results have confirmed the requirement of perfect antiperiplanar geometry of the eliminating groups, SiMe3 and β-OH. The quantitation of the hydrolysis products, the cycloalkanones, was done using the gas chromatographic peak area normalization method using an internal standard. The rate data obtained at three different temperatures were employed to calculate ΔH‡, ΔS‡, and ΔG‡. The rate constants and thermodynamic parameters increase with the ring size. There is an interesting demarcation between these two values for common ring silyldiols and the larger ring silyldiols.
研究了酸催化下环状顺式α,β-二羟基
硅烷 3-8 通过消除
硅醇生成环烷酮的反应,在三种不同温度(298, 313 和 328 K)下进行。
硅二醇 3-7 反应顺利
水解,而 8 对
水解有抵抗力。消除反应的易度(通过速率常数反映)与环的构象灵活性和分子内氢键有关。研究结果确认了消除基团 SiMe3 和 β-OH 之间完美反式平面几何的要求。通过使用内标的气相色谱峰面积归一化方法,对
水解产物环烷酮进行了定量。获得的三种不同温度下的速率数据用于计算 ΔH‡、ΔS‡ 和 ΔG‡。速率常数和热力学参数随着环的大小增加而增加。对于常见环的
硅二醇和较大环的
硅二醇之间存在一个有趣的划分。