采用分子动力学模拟方法对298 K,0.78 g/cm3的液态甲醇的蒸发潜热、自扩散系数、体系的微观构型、径向分布函数和甲醇分子间的氢键结构进行了模拟研究.结果表明,甲醇的蒸发潜热和自扩散系数的模拟结果与实验数据符合.采用计算机图形技术得到了体系达到平衡时其微观构型的物理图像;对氢键的结构分析表明,形成两氢键的甲醇分子的摩尔分数为77.39%,每一甲醇分子形成氢键的平均数目为1.902;形成氢键的两甲醇分子O…O—H取向角分布曲线在12.2°处出现峰值,取向角θ小于12.2°的甲醇分子的摩尔分数为57.39%,形成氢键的甲醇分子取向几乎呈线性分布;氢键的平均寿命为12.6 ps.
Molecular dynamics simulations of liquid water were performed at 258 K and density of 1.0 g/cm^3 under different strengths of an external electric field, ranging from 0 to 8.0×10^9V/m, to investigate the influence of an external field on structural and dynamic properties of water. The flexible simple point charge model is used for water molecules. An enhancement of the water hydrogen bond structure with increasing strength of the electric field has been deduced from the radial distribution functions and the analysis of hydrogen bond structure. With increasing field strength, water system has a more perfect structure, which is shnilar to ice structure. However, the electrofreezing phenomenon of liquid water has not been detected because of a too large self-diffusion coefficient. The self-diffusion coefficient decreases remarkably with increasing strength of electric field, and the self-diffusion coefficient is anisotropic.
A visualization system based on microscopy,photoelectric imaging analysis and digital processing was developed to investigate the micrometer-level mass transfer process of polyvinylpyrrolidone(PVP)across the interface of dichloromethane-water.The concentration-gray scale standard curves were obtained by measuring the gray scales of the images of 10 PVP dichloromethane solutions with different concentrations.The concentrations of PVP corresponding to different times were determined by measuring the gray scales of the images of PVP dichloromethane solutions at the corresponding times.The mass transfer kinetics curve of PVP across the interface of dichloromethane-water was then obtained.In addition,the evolution of flow field in the dichloromethane phase near the interface was observed and analyzed via the visualization system.
A novel technique combining photoelectronic microscopy and computer imaging tracing was used to investigate the synthesis of thioether(2-[3-methyl-4-(2,2,2-trifluoro-ethoxy)-pyridine-2-(methylsulfanyl)]-1H-benzoimidazole),which is an intermediate for lansoprazole.Visualization in sub-microcosmic surroundings was realized to study interfacial phenomenon.The reaction kinetics study by a visualization technique was carried out in a mini-reactor,and the concentration-gray scale standard curves for thioether were obtained by analyzing the gray scales of digital images.Based on the concentration-gray scale standard curves,the reactant concentrations at different times were calculated,and the reaction kinetics curve and reaction rate equation were obtained.Also the total mass-transfer resistance from bulk phase to interface of sodium imidazole and bromopyridine was obtained.Liquid-liquid interface of synthesizing thioether was observed and its mass transfer mechanism was discussed.
