实验和计算热化学：2-羟基苯甲酸烷基酯（水杨酸酯）的分子内氢键有多强,Physical Chemistry Chemical Physics

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实验和计算热化学：2-羟基苯甲酸烷基酯（水杨酸酯）的分子内氢键有多强
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2023-07-24 , DOI: 10.1039/d3cp01677c
Sergey P Verevkin _{1,

2} , Svetlana V Portnova ₃ , Vladimir N Emel'yanenko ₁ , Ruslan N Nagrimanov ₂ , Mikhail A Varfolomeev _{2,

4}

Affiliation

氢键（HB）是一种令人着迷的现象，在有机和生物分子中表现出不寻常的特性。氢键的定性表现在许多化学过程中是已知的。然而，量化 HB 强度是一项具有挑战性的任务，特别是在分子内氢键的情况下。2-羟基苯甲酸烷基酯具有很强的intra-HB，这一点在定性上已得到证实。适合测定HB内强度的热化学方法是本研究的重点。2-羟基苯甲酸烷基酯（包括甲基、乙基、正丙基和正丁基）在298.15 K下的实验气相形成焓是通过蒸气压测量和高精度燃烧量热法得出的，并通过量子化学方法进行了验证G3MP2 和 G4。2-羟基苯甲酸甲酯中的HB内强度是通过平衡反应、“对位-邻位”方法和“HB”比较顺式和反式构象异构体的能量，根据评估的气相形成焓来确定的。并出”方法。所有这些方法给出的分子内氢键强度的共同水平为-43 kJ mol ^-1。发现HB内强度与2-羟基苯甲酸烷基酯的链长无关。

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Experimental and computational thermochemistry: how strong is the intramolecular hydrogen bond in alkyl 2-hydroxybenzoates (salicylates)

Hydrogen bonding (HB) is a fascinating phenomenon that exhibits unusual properties in organic and biomolecules. The qualitative manifestation of hydrogen bonds is known in numerous chemical processes. However, quantifying HB strength is a challenging task, especially in the case of intra-molecular hydrogen bonds. It is qualitatively well established that the alkyl 2-hydroxybenzoates have strong intra-HB. The thermochemical methods suitable for the determination of intra-HB strength were the focus of this study. The experimental gas phase formation enthalpies for alkyl 2-hydroxybenzoates (including methyl, ethyl, n-propyl and n-butyl) at 298.15 K were derived from a combination of vapour pressure measurements and high-precision combustion calorimetry and validated by the quantum chemical methods G3MP2 and G4. The intra-HB strength in methyl 2-hydroxybenzoate was determined from the evaluated gas-phase enthalpies of formation by comparing the energies of cis- and trans- conformers, by well-balanced reactions, the “para–ortho” method and the “HB and Out” method. All these methods give a common level of intra-molecular hydrogen bond strength of −43 kJ mol⁻¹. The intra-HB strength was found to be independent of the chain length of the alkyl 2-hydroxybenzoates.

更新日期：2023-07-24

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