Swiatla-Wojcik Dorota
Institute of Applied Radiation Chemistry, Lodz University of Technology, Zeromskiego 116, 90-924 Lodz, Poland.
Molecules. 2024 Nov 21;29(23):5513. doi: 10.3390/molecules29235513.
Pressurized high-temperature water attracts attention as a promising medium for chemical synthesis, biomass processing or destruction of hazardous waste. Adjustment to the desired solvent properties requires knowledge on the behavior of populations of hydrogen-bonded molecules. In this work, the interconnection between the hydrogen bond (HB) dynamics and the structural rearrangements of HB networks have been studied by molecular dynamics simulation using the modified central force flexible potential and the HB definition controlling pair interaction energy, HB length and HB angle. Time autocorrelation functions for molecular pairs bonded continuously and intermittently and the corresponding mean lifetimes have been calculated for conditions ranging from ambient to supercritical. A significant reduction in the continuous and intermittent lifetimes has been found between (293 K, 0.1 MPa) and (373 K, 25 MPa) and attributed to the decreasing size of patches embedded in the continuous HB network. The loss of global HB connectivity at ca. (573 K, 10 MPa) and the investigated supercritical conditions do not noticeably affect the HB dynamics. Over the whole temperature range studied, the reciprocal intermittent lifetime follows the transition state theory dependence on temperature with the activation energy of 10.4 kJ/mol. Calculations of the lifetime of molecules that do not form hydrogen bonds indicate that at supercritical temperatures, the role of reactions involving an unbound HO molecule as a reactant can be enhanced by lowering system density.
加压高温水作为一种用于化学合成、生物质处理或有害废物销毁的有前景的介质而受到关注。要将溶剂性质调整到所需状态，需要了解氢键分子群体的行为。在这项工作中，通过分子动力学模拟，使用修正的中心力柔性势和控制配对相互作用能、氢键长度和氢键角度的氢键定义，研究了氢键（HB）动力学与氢键网络结构重排之间的相互联系。针对从环境条件到超临界条件的各种情况，计算了连续和间歇键合分子对的时间自相关函数以及相应的平均寿命。发现在（293 K，0.1 MPa）和（373 K，25 MPa）之间，连续和间歇寿命显著缩短，这归因于嵌入连续氢键网络中的斑块尺寸减小。在约（573 K，10 MPa）以及所研究的超临界条件下，整体氢键连通性的丧失并未明显影响氢键动力学。在所研究的整个温度范围内，间歇寿命的倒数遵循过渡态理论对温度的依赖性，活化能为(10.4) kJ/mol。对不形成氢键的分子寿命的计算表明，在超临界温度下，通过降低系统密度，可以增强涉及未结合的HO分子作为反应物的反应的作用。
