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Spatial Separation of Molecular Conformers and Clusters
Published on: January 9, 2014
异构效应与体阻碍在质子型葡萄糖氨和环氨中对离子溶解的作用
Charles L Perrin1, Joshua Kuperman
1Department of Chemistry, University of California-San Diego, La Jolla, California 92093-0506, USA. cperrin@ucsd.edu
Journal of the American Chemical Society
|July 17, 2003
概括
反向的异构效应尚未得到充分理解. 这项研究表明,固体阻碍,而不是反向的异体效应,驱动了对质子型葡萄糖氨酸的赤道偏好,澄清了异体效应.
科学领域:
- 碳水化合物的化学成分
- 有机化学 有机化学
- 物理有机化学 有机化学
背景情况:
- 反向的异构效应描述了皮拉诺环上对赤道位置的阴离子替代物偏好.
- 这种现象与现有的分子结构理论和先前的实验证据相矛盾.
- 研究这种效应对于理解碳水化合物的立体化学和反应性至关重要.
研究的目的:
- 为了研究N-O-methylglucopyranosyl) anilines的异构平衡中的N-质子化诱导的变化.
- 为了比较这些转变与观察到的N- ((4-tert-butylcyclohexyl) anilines的转变,以了解硬质和电子影响.
- 阐明异构效应的替代因子依赖性,并挑战逆异构效应的概念.
主要方法:
- 利用高精度的NMR定位来比较混合物中α和β异常体的基本性.
- 在葡萄糖氨衍生物中测量了因N-质子化诱导的异构平衡变化.
- 测量了N-质子化诱导的 cis/trans 平衡的转移,用于循环氨林衍生物的比较.
主要成果:
- 质子转移平衡向赤道位置在葡萄糖氨和环氨系列,与固态阻碍离子溶解一致.
- 葡萄糖氨酸的转移小于循环氨酸,这表明增强了正常的无分子效应,抵消了硬质障碍.
- 循环氨林的取电子替代剂增加了赤道偏移,而葡萄糖氨林的替代剂减少了它,支持正常的异构效应模型.
结论:
- 观察到的赤道偏好主要是由固态阻碍溶解驱动的,而不是反向的异构效应.
- 葡萄糖氨酸中增强的正常体效应减轻了体的影响.
- 该研究定义了异构效应的替代依赖性,强调电子和固态因素而不是反向异构效应.
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