Intramolecular Hydrogen Bonding and Cooperative Interactions in Carbohydrates via the Molecular Tailoring Approach

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• 作者：Milind M. Deshmukh ; Libero J. Bartolotti ; Shridhar R. Gadre
• 刊名：Journal of Physical Chemistry A
• 出版年：2008
• 出版时间：January 17, 2008
• 年：2008
• 卷：112
• 期：2
• 页码：312 - 321
• 全文大小：338K
• 年卷期：v.112,no.2(January 17, 2008)
• ISSN：1520-5215

文摘

In spite of many theoretical and experimental attempts for understanding intramolecular hydrogen bonding(H-bonding) in carbohydrates, a direct quantification of individual intramolecular H-bond energies and thecooperativity among the H-bonded networks has not been reported in the literature. The present work attempts,for the first time, a direct estimation of individual intramolecular O-H···O interaction energies in sugarmolecules using the recently developed molecular tailoring approach (MTA). The estimated H-bond energiesare in the range of 1.2-4.1 kcal mol^-1. It is seen that the OH···O equatorial-equatorial interaction energieslie between 1.8 and 2.5 kcal mol^-1, with axial-equatorial ones being stronger (2.0-3.5 kcal mol^-1). Thestrongest bonds are nonvicinal axial-axial H-bonds (3.0-4.1 kcal mol^-1). This trend in H-bond energies isin agreement with the earlier reports based on the water-water H-bond angle, solvent-accessible surface area(SASA), and ¹H NMR analysis. The contribution to the H-bond energy from the cooperativity is also estimatedusing MTA. This contribution is seen to be typically between 0.1 and 0.6 kcal mol^-1 when H-bonds are apart of a relatively weak equatorial-equatorial H-bond network and is much higher (0.5-1.1 kcal mol^-1)when H-bonds participate in an axial-axial H-bond network.