Study on the specific Solvent Effects on Carbocation Reactions

特定溶剂对碳正离子反应影响的研究

基本信息

批准号：
10440188
负责人：
TAKEUCHI Ken'ichi
金额：
$ 7.55万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

(1) Specific solvent effects in the generation-step of carbocationsThe polarity effect that controls the solvolysis rates has been recognized as a linear free energy relationship, the so-called Grunwald-Winstein relationship. However, it has been shown that some substrates having a bulky hydrocarbon group show unusually slow rates of solvolysis and curved Grunwald-Winstein plots. The hydrophobic effect has been suggested as a probable origin of this behavior.(2) Specific solvent effects in the reacting-step of carbocationsThe first example was found for the elimination reaction that gives a propellane-type product after deprotonation of a cage-shaped, bridgehead carbocation. This reaction is markedly dependent upon the basicity of solvent and difficultly occurs in acidic solvents. Moreover, the deprotonation has only been found for the so-called α-keto cations.(3) Specific solvent effects in the ionic dissociation of a C-C σ bondNovel fullerene derivatives t-BuCィイD260ィエD2R were synthesized from stable hydrocarbon anion t-BuCィイD3-(/)60ィエD3 and substituted cyclopropenylium ions RィイD1+ィエD1. These hydrocarbons ionize in THF in the presence of small amounts of added DMSO. It was revealed that the Lewis-base type specific solvation of DMSO molecules facilitates the ionic dissociation.(4) Specific solvent effects on the stability of hydrocarbon anionsIt was revealed that the gas-phase stability of cyclopentadienide anion increases on introduction of alkyl substituents or condensed aromatic rings, whereas it decreases in solution. From these observations, the stabilization effect of solvent toward the cyclopentadienide anion has been quantitatively evaluated. The effect of alkyl and aromatic substituents to lower the anion stability in solution has also been quantitatively assessed.

（1）在碳化物的生成阶段的特定溶解性效应控制溶剂溶解速率的极性效应已被认为是线性自由能关系，即所谓的Grunwald-Winstein关系。但是，已经表明，一些具有笨重的碳氢化合物基团的底物表现出异常缓慢的溶解度和弯曲的Grunwald-Winstein图。疏水作用已被认为是这种行为的有问题的起源。（2）在碳化反应阶段的特定偿付能力效应中，发现了第一个示例以消除反应，该反应在脱落笼子形的桥头，桥头形的碳化后提供了丙烷型产物。该反应明显取决于溶解度的碱性，并且在酸性溶液中很难发生。此外，仅在所谓的α-酮阳离子中发现了去质子化。（3）从稳定的液压碳含液能碳anion t-bucii d3-（替代品）中综合了c-cσ键源富勒烯衍生物T-bucii d260e d2r在离子离子解离中的特定溶剂效应。 D1+E D1。在少量添加的DMSO的情况下，这些碳氢化合物在THF中电离。结果表明，DMSO分子的Lewis-base类型特异性溶液促进了离子解离。（4）特异性溶剂对烃类阴离子稳定性的特异性影响表明，环戊二烯阴离子的气相稳定性在引入烷基亚位点的引入时增加了溶液或抑制均应溶液，以下均为下降。从这些观察结果中，已经对溶剂对环戊二烯阴离子的稳定作用进行了定量评估。烷基和芳族亚能力降低溶液中的阴离子稳定性的影响也已进行了定量评估。