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Studies on the effects of substituents on the gas-phase reactions of charged phenyl radicals with allyl iodide, hydrogen atom donors, nitroxides, dienes and small peptides by using mass spectrometry

机译：质谱法研究取代基对带电苯基与烯丙基碘，氢原子供体，氮氧化物，二烯和小肽的气相反应的影响

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摘要

This research probes the factors that control radical reactions of charged phenyl radicals in the gas phase by using FT-ICR mass spectrometry. In the first two studies, the ability of differently substituted phenyl radicals to abstract an iodine atom from allyl iodide and a hydrogen atom from tetrahydrofuran and tributyltin hydride was systematically examined. Neutral electron-withdrawing substituents were found to increase the reaction efficiencies by lowering the energy of the transition state. The extent of rate enhancement depends on the type and number of substituents, as well as their location relative to the radical site. Computational results indicate that variations in the transition state energy are explained by polar effects arising from a stabilizing charge transfer resonance structure of the transition state, rather than by variations in the thermodynamic driving force. In the third study, substituent effects on radical-radical recombination reactions were explored. While substituents do not have a major influence on the recombination efficiency, presumably due to a low reaction barrier, the product distribution is greatly impacted. The fourth study focuses on hydrogen atom abstraction and addition-elimination reactions of phenyl radicals with 1,4-cyclohexadiene. The different fragmentation mechanisms of the addition-elimination reactions are discussed. The fifth study examines the effects of the type of the charge site on reactions of substituted phenyl radicals. The results lead to the prediction that neutral phenyl radicals are likely to show similar substituent effect trends. Additionally, the effects of substituents on the reactions of a phenyl radical containing a negative charge site are examined. In the final study, the above approaches were applied to the reactions of phenyl radicals with amino acids and small peptides.
机译：这项研究通过使用FT-ICR质谱仪探索了控制气相中带电苯基自由基的自由基反应的因素。在前两项研究中，系统地研究了不同取代的苯基自由基从烯丙基碘中提取碘原子，从四氢呋喃和氢化三丁基锡中提取氢原子的能力。发现中性的吸电子取代基通过降低过渡态的能量来提高反应效率。速率提高的程度取决于取代基的类型和数量，以及它们相对于自由基位点的位置。计算结果表明，过渡态能量的变化是由稳定的过渡态电荷转移共振结构引起的极性效应解释的，而不是由热力学驱动力的变化解释的。在第三项研究中，研究了取代基对自由基-自由基复合反应的影响。尽管取代基对重组效率没有主要影响，但大概是由于低的反应势垒，产物的分布受到很大影响。第四个研究集中在氢原子的提取和苯基与1,4-环己二烯的加成消除反应上。讨论了加成消除反应的不同裂解机理。第五项研究考察了电荷位点类型对取代苯基自由基反应的影响。结果导致预测，中性苯基可能会显示出相似的取代作用趋势。另外，研究了取代基对含有负电荷位的苯基自由基反应的影响。在最后的研究中，上述方法被应用于苯基自由基与氨基酸和小肽的反应。

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  • 作者

    Heidbrink, Jenny Lea.;

  • 作者单位

    Purdue University.;

  • 授予单位 Purdue University.;
  • 学科 Analytical chemistry.;Organic chemistry.;Physical chemistry.
  • 学位 Ph.D.
  • 年度 2001
  • 页码 162 p.
  • 总页数 162
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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