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首页> 外文学位 >Advances in carbocation chemistry: Carbocations in ionic liquids, beta-silyl cyclopropyl carbocations, and beta- and gamma-silyl cyclobutyl carbocations.
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Advances in carbocation chemistry: Carbocations in ionic liquids, beta-silyl cyclopropyl carbocations, and beta- and gamma-silyl cyclobutyl carbocations.

机译：碳正离子化学的进展：离子液体中的碳正离子，β-甲硅烷基环丙基碳正离子，β-和γ-甲硅烷基环丁基碳正离子。

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This dissertation describes studies encompassing a variety of areas of carbocation chemistry. Carbocation formation in ionic liquids, which are polar aprotic solvents, was studied. The chemistry of some unusual silicon substituted carbocations was also investigated.;Some unusual reactivity was seen in ionic liquids as well. For example, it was found that small concentrations of water in the ionic liquids have a significant impact on the rates of solvolyses of mesylates. The effect of water on triflate solvolyses however, was negligible. Additionally, a novel oxidation process of triflates involving loss of sulfinate was found to occur in certain ionic liquids.;An investigation of the stabilizing effect of beta-silyl groups on cyclopropyl carbocations was also undertaken. The normally large effect of a beta-silyl group (which can cause solvolysis rate enhancements of up to 1012) was found to be greatly repressed in cyclopropyl systems. Computational studies agreed with this conclusion. The intermediate silyl-substituted cyclopropyl cations instead tended to undergo ring opening since silyl stabilization is reduced.;A similar study was undertaken involving cyclobutyl carbocations. Incorporation of a beta-silyl group into cyclobutyl carbocations led again to a smaller than expected beta-silyl stabilization. In fact, the effect was successfully quashed in a beta-silyl benzocyclobutenyl carbocation in which beta-silyl stabilization would have led to antiaromatic character in the carbocation.;Reactions of a number of triflates, mesylates and trifluoroacetates in ionic liquids have been investigated. It was concluded that these substrates all react via carbocationic intermediates. In fact, some of the ionic liquids under investigation were found to have an ionizing power similar to that of CF3CH2OH, a commonly used solvent for carbocation formation. Evidence in support of this conclusion include the observation of carbocationic rearrangements in a variety of substrates, a Hammett-Brown rho+ value of --7.1 for the solvolyses of 1-aryl-2,2,2-trifluoroethyl triflates, and the facile solvolysis of 1-adamantyl mesylate which necessarily proceeds via a carbocationic intermediate.;The gamma-silyl effect was also investigated in cyclobutyl systems. Experimental and computational studies showed that gamma-silyl stabilization can occur via two distinct modes. Either the front, or the rear lobe of the gamma-silyl group can donate electron density into the empty p-orbital of the carbocation. This effect was also found to be much larger than previously recorded.
机译：本文描述了涵盖碳正离子化学各个领域的研究。研究了极性非质子溶剂离子液体中的碳正离子形成。还研究了一些不寻常的硅取代的碳正离子的化学反应。在离子液体中也观察到了一些不寻常的反应性。例如，发现离子液体中的低浓度水对甲磺酸酯的溶剂分解速率具有显着影响。然而，水对三氟甲磺酸盐溶剂化的影响可忽略不计。此外，发现在某些离子液体中发生了三氟甲磺酸的新氧化过程，涉及亚磺酸盐的损失。;还研究了β-甲硅烷基对环丙基碳正离子的稳定作用。发现在环丙基系统中，β-甲硅烷基的通常较大的作用（可导致溶剂分解速率提高至1012）被大大抑制。计算研究同意这一结论。相反，由于甲硅烷基的稳定性降低，中间体甲硅烷基取代的环丙基阳离子倾向于开环。进行了涉及环丁基碳阳离子的类似研究。将β-甲硅烷基结合到环丁基碳阳离子中，再次导致小于预期的β-甲硅烷基稳定度。实际上，在β-甲硅烷基苯并环丁烯基碳正离子中，这种作用已被成功消除，其中β-甲硅烷基的稳定化将导致碳正离子中的抗芳烃特性。现已研究了离子液体中许多三氟甲磺酸酯，甲磺酸酯和三氟乙酸酯的反应。结论是这些底物都通过碳阳离子中间体反应。实际上，已发现某些正在研究的离子液体的电离能力与CF3CH2OH（一种通常用于碳阳离子形成的溶剂）的电离能力相似。支持该结论的证据包括观察到各种底物中的碳正离子重排，1-芳基-2,2,2-三氟乙基三氟甲磺酸酯的溶剂分解的Hammett-Brown rho +值为--7.1和容易地溶剂分解甲磺酸1-金刚烷基酯必须通过碳阳离子中间体进行反应。在环丁基体系中也研究了γ-甲硅烷基效应。实验和计算研究表明，γ-甲硅烷基的稳定作用可以通过两种不同的方式发生。 γ-甲硅烷基的前叶或后叶均可将电子密度提供给碳正离子的空p轨道。还发现此效果比以前记录的要大得多。

著录项

  • 作者

    Willis-Kochly, Elizabeth D.;

  • 作者单位

    University of Notre Dame.;

  • 授予单位 University of Notre Dame.;
  • 学科 Chemistry Organic.
  • 学位 Ph.D.
  • 年度 2008
  • 页码 275 p.
  • 总页数 275
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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