Institute of Molecular Physics, Polish Academy of Sciences, M. Smoluchowskiego 17, 60-179 Poznań, Poland.
Phys Chem Chem Phys. 2012 Mar 7;14(9):3170-5. doi: 10.1039/c2cp23960d. Epub 2012 Jan 31.
The paper presents the experimental verification of the result obtained with the molecular dynamics simulation which revealed the differences in the topology of the hydrogen-bonded networks in liquid formamide and water, namely, the differences in their intermolecular cyclization process (I. Bakó, et al. J. Chem. Phys. 2010, 132, 014506). It is shown in our paper that the difference in the (simulated) size distribution of the hydrogen-bonded molecular rings in water (a relatively sharp maximum at about 6 molecules) and formamide (a broad maximum at about 11 molecules) strongly manifests itself in the experimental values of the Kirkwood correlation factor of the compounds. A much larger number of molecules included in the cyclic species (of more or less compensated dipole moment) leads to significant decrease of the Kirkwood correlation factor of formamide in comparison to that of water. Besides, as a consequence of an enhancement in formation of the cyclic multimers of formamide, one observes an essential reduction of the orientational entropy increment of that liquid, in comparison to the entropy effect related to liquid amides where the chain multimers are formed.
本文对分子动力学模拟结果进行了实验验证，该结果揭示了液态甲酰胺和水中氢键网络拓扑结构的差异，即它们的分子内环化过程的差异（I. Bakó 等人，J. Chem. Phys. 2010, 132, 014506）。本文表明，氢键分子环在水中（约 6 个分子处有一个相对尖锐的最大值）和甲酰胺（约 11 个分子处有一个宽的最大值）的（模拟）大小分布的差异在化合物的 Kirkwood 相关因子的实验值中表现得非常明显。包含在环状物质（具有或多或少补偿偶极矩）中的分子数量较多，会导致甲酰胺的 Kirkwood 相关因子比水的显著降低。此外，由于甲酰胺的环状多聚物的形成增强，与形成链状多聚物的酰胺类液体的熵效应相比，观察到该液体的取向熵增量显著降低。
