Torsional effects on the one-bond 13C-13C spin coupling constant in ethylene glycol: Insights into the behavior of 1JCC in carbohydrates†
Torsional effects on the one-bond 13C-13C spin coupling constant in ethylene glycol: Insights into the behavior of 1JCC in carbohydrates†
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乙二醇中单键 13C-13C 自旋耦合常数的扭转效应：深入了解 1JCC 在碳水化合物中的行为†
DOI：
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发表时间：
1993
期刊：
影响因子：
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通讯作者：
A. Serianni
中科院分区：
文献类型：
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作者：
I. Carmichael;D. Chipman;C. Podlasek;A. Serianni
最近对一系列富含[sup 13] C的碳水化合物及其衍生物的NMR研究表明，OH-C-C-OH片段中的[sup 1]J[sub CC]受C-C二面角的影响。在这项研究中，通过测量和计算简单模型化合物中的[sup 1]J[sub CC]值，详细探讨了这种相关性和其他相关性。通过比较各种计算和实验[sup 1]J[sub CC]的绝对值和观察到的趋势，验证了所使用的从头计算方法。在QCISD（T）水平上对电子关联进行了全面处理，得到了与实验符合较好的结果。虽然[sup 1]J[sub CC]值计算的SCF水平比实验观察到的大得多，电子相关校正保持相对独立的构象，使SCF计算是非常有用的检查趋势。乙烷，乙醇，乙二醇，和乙醇醛水合物的结果表明，[sup 1]J[sub CC]增加的CC片段上的羟基取代基的数量。[sup 1]J[sub CC]对乙二醇中C-C扭转的依赖性的计算与碳水化合物的实验数据一致，表明当羟基取代基为反式时耦合最大，并且对于gauche几何形状较小。这项研究中一个重要的新发现是，乙二醇片段中的[sup 1]J[sub CC]在更大程度上取决于C-O扭转，当羟基质子与碳原子相反时达到最大值，而在笨拙构型中达到最小值。参考文献61篇，图5，5片。«少
Recent NMR studies of a series of [sup 13]C-enriched carbohydrates and their derivatives have revealed that [sup 1]J[sub CC] in OH-C-C-OH fragments is affected by the C-C dihedral angle. This and other related correlations are explored in detail in this study by measuring and computing [sup 1]J[sub CC] values in simple model compounds. The ab initio computational methods used are validated through a comparison of absolute values and trends observed for a variety of calculated and experimental [sup 1]J[sub CC]. Good agreement with experiment is found when electron correlation is thoroughly treated at the sophisticated QCISD(T) level. Although [sup 1]J[sub CC] values computed at the SCF level are much larger than those observed experimentally, the electron correlation corrections remain relatively independent of conformation, so that SCF calculations are very useful for examining trends. Results for ethane, ethanol, ethylene glycol, and glycolaldehyde hydrate indicate that [sup 1]J[sub CC] increases with the number of hydroxyl substituents on the CC fragment. Calculations of the dependence of [sup 1]J[sub CC] on C-C torsion in ethylene glycol agree with experimental data for carbohydrates, indicating that the coupling is largest when the hydroxyl substituents are trans and smaller for gauche geometries. A significant new finding inmore » this study is that [sup 1]J[sub CC] in ethylene glycol fragments depends to an even larger extent on the C-O torsions, reaching a maximum when the hydroxyl proton is anti to a carbon and a minimum in gauche configurations. 61 refs., 5 figs., 5 tabs.« less