Gas-phase acidity of D-glucose. A density functional theory study
Gas-phase acidity of D-glucose. A density functional theory study
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DOI：
10.1002/jms.671
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发表时间：
2004-08-01
影响因子：
2.3
通讯作者：
Tortajada, J
中科院分区：
文献类型：
--
作者：
Salpin, JY;Tortajada, J
用B3 LYP方法结合6- 31 G（d，p）或6-31+G（d，p）标准基组研究了D-吡喃葡萄糖的气相酸性。对于每种端基异构体，考虑各种伯羟基和仲羟基的去质子化。在溶液中，异头羟基被发现是最酸性的两种异头物，但只有当6-31+G（d，p）基组用于几何优化。异头羟基的去质子化诱导了重要的C（1）-O内环键的伸长，并随后促进了能量上有利的开环过程，这一点由非常小的计算活化能垒证明。结果还表明，各种去质子化的α-和β-端基异构体之间的相互转化可能很容易发生在稍微高能的条件下。用B3 LYP/6-311+G（2df，2 p）方法计算得到该化合物的绝对气相酸度Δ（酸）G（298）（o）（α-D-葡萄糖）= 1398 kJ mol（-1）。这一估计值与迄今为止唯一的实验值吻合得很好。最后，这项研究再次证实，使用重原子上的扩散功能是必要的，以正确地描述阴离子系统，并实现良好的相对和绝对的气相酸度。版权所有（C）2004约翰威利父子有限公司。
The gas-phase acidity Of D-glucopyranose was studied by means of B3LYP calculations combined with 6-31G(d,p) or 6-31+G(d,p) standard basis sets. For each anomer, deprotortation of the various primary and secondary hydroxyl groups was considered. As in solution, the anomeric hydroxyl is found to be the most acidic for both anomers, but only when the 6-31+G(d,p) basis set is used for geometry optimization. Deprotonation of the anomeric hydroxyl induces an important C(1)-O endocyclic bond elongation and subsequently promotes an energetically favored ring-opening process as attested by the very small calculated activation barriers. The results also suggest that interconversion between the various deprotonated alpha- and beta-anomers may easily occur under slightly energetic conditions. B3LYP/6-311+G(2df,2p) calculations led to the an absolute gas-phase acidity of Delta(acid) G(298)(o) (alpha-D-glucose) = 1398 kJ mol(-1). This estimate matches well the only experimental value available to date. Finally, this study again confirms that the use of diffuse functions on heavy atoms is necessary to describe anionic systems properly and to achieve good relative and absolute gas-phase acidities. Copyright (C) 2004 John Wiley Sons, Ltd.