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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >An Experimental and Computational Study of the Gas-Phase Structures of Five-Carbon Monosaccharides
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An Experimental and Computational Study of the Gas-Phase Structures of Five-Carbon Monosaccharides

机译：五碳单糖气相结构的实验和计算研究

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摘要

The gas-phase structures of five five-carbon monosaccharides (D-ribose, D-lyxose, 2-deoxy-D-ribose, D-xylose, and D-arabinose) were studied via ion-molecule reactions with dimethoxyphosphenium ion and 1,3-dioxolane-2-phosphenium ion in a Fourier transform ion cyclotron resonance mass spectrometer. These reagent ions have been earlier demonstrated to be sensitive to the three-dimensional structures of diastereomeric vicinal diols. They were found to display unique reactivity toward each monosaccharide. The results indicate that the gaseous monosaccharides are cyclic molecules. On the basis of a comparison of the reactions of monosaccharides introduced into the gas phase via two different methods, laser-induced acoustic desorption (LIAD) and thermal desorption, the monosaccharides are concluded to maintain their crystalline structure, a pyranose form, throughout the evaporation procedure. For all the monosaccharides in this study except for D-lyxose, the lowest-energy structure found computationally using density functional theory (B3LYP/6-311++G(d,p)) is a pyranose form that lies at least 1.7 kcal/mol lower in energy than the corresponding lowest-energy furanose form. For D-lyxose, however, a furanose form was calculated to be lower in energy than the pyranose form albeit only by 0.1 kcal/mol. These computational results suggest that a pyranose form indeed is likely to be the dominant form of the monosaccharides in the gas phase. Several possible factors controlling the relative stability of each monosaccharide isomer in the gas phase were examined computationally. The order of importance of these factors in determining the relative stabilities was found to be as follows: intramolecular hydrogen bonding interaction anomeric > steric (axial/equatorial) factors Δ2 effect.
机译：通过与二甲氧基phosph离子和1的离子分子反应研究了5个五碳单糖（D-核糖，D-糖，2-脱氧-D-核糖，D-木糖和D-阿拉伯糖）的气相结构。傅里叶变换离子回旋共振质谱仪中的3-二氧戊环-2-phosph离子这些试剂离子已被较早地证明对非对映体邻位二醇的三维结构敏感。发现它们对每种单糖显示出独特的反应性。结果表明气态单糖是环状分子。根据对通过两种不同方法引入气相的单糖反应的比较，即激光诱导的声解吸（LIAD）和热解吸，可以得出结论，在整个蒸发过程中，单糖保持其晶体结构（吡喃糖形式）程序。对于本研究中的所有单糖（D-糖），使用密度泛函理论（B3LYP / 6-311 ++ G（d，p））计算得出的最低能量结构为吡喃糖形式，其至少为1.7 kcal /摩尔比相应的最低能量的呋喃糖形式的能量低。然而，对于D-lyxose，计算得出呋喃糖形式的能量比吡喃糖形式低，尽管仅为0.1 kcal / mol。这些计算结果表明，在气相中，吡喃糖形式确实可能是单糖的主要形式。通过计算检查了控制气相中每个单糖异构体的相对稳定性的几种可能因素。发现这些因素在确定相对稳定性中的重要性顺序如下：分子内氢键相互作用端基异构体>空间（轴向/赤道）因子Δ2效应。

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