使用平衡同位素效应来检测分子内OH/OH键:结构和溶剂效应
Thomas E Vasquez1, Jon M Bergset, Matthew B Fierman
1Department of Chemistry, Pomona College, 645 North College Avenue, Claremont, CA 91711, USA.
Journal of the American Chemical Society
|March 21, 2002
概括
在不同的溶剂中,分子内键表现出相反的同位素转移信号. 乳更喜欢分子间的键,而化-d(5) 放大了配置分配的变化.
科学领域:
- 核磁共振光谱学 核磁共振光谱学
- 物理有机化学 有机化学
- 超分子化学 超分子化学
背景情况:
- 二醇中的分子内键会影响它们的化学特性.
- 在NMR光谱中的平衡同位素转移对结环境敏感.
- 溶剂效应显著影响键强度和NMR化学转移.
研究的目的:
- 研究溶剂极性和结能力对部分化二醇中平衡同位素转移的影响.
- 阐明键几何学与NMR同位素转移的标志和大小之间的关系.
- 探索不同化溶剂在配置分配和键检测方面的实用性.
主要方法:
- 部分脱的1,3-和1,4-二醇的比较性 (1) H NMR光谱.
- 使用各种接受键 (DMSO-d6),乙-d6),THF-d8和非极性 (CD2Cl2 ,-d6) 的化溶剂.
- 使用pyridine-d(5) 作为一种溶剂来放大同位素转移.
主要成果:
- 在接受键的溶剂中观察到平衡同位素转移的标志反转,归因于竞争性的分子间键和限制化学转移.
- 量化对分子间溶剂键的偏好 (10.9 +/- 0.5 cal/mol在DMSO-d6中对于1,4-diol).
- 证明了pyridine-d(5) 能够放大正同位素转移 (高达3倍) 的能力,用于配置赋值 (2,4-pentanediol) 和检测分子内键 (cyclodextrins).
- 在非极性溶剂中确定了负 (上场) 同位素转移,在-d6中观察到更大的转移,这对配置分析很有用.
结论:
- 分子内键的几何结构决定了平衡同位素转移的标志,由溶剂相互作用调节.
- 具有与溶剂分子形成分子间键的偏好.
- 化和非极性溶剂是基于NMR的结构阐释的宝贵工具,包括配置赋值和键网络的研究.
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