Effects of Ionic Liquids on the Thermodynamics of Hydrogen Activation by Frustrated Lewis Pairs: A Density Functional Theory Study**

Nowadays, hydrogen activation by frustrated Lewis pairs (FLPs) and their applications are one of the emerging research topics in the field of catalysis. Previous studies have shown that the thermodynamics of this reaction is determined by electronic structures of FLPs and solvents. Herein, we investigated systems consisting of typical FLPs and ionic liquids (ILs), which are well known by their large number of types and excellent solvent effects. The density functional theory (DFT) calculations were performed to study the thermodynamics for H₂ activation by both inter- and intra-molecular FLPs, as well as the individual components. The results show that the computed overall Gibbs free energies in ILs are more negative than that computed in toluene. Through the thermodynamics partitioning, we find that ILs favor the H−H cleavage elemental step over the elemental steps of proton attachment, hydride attachment and zwitterionic stabilization. Moreover, the results show that these effects are strongly dependent on the type of FLPs, where intra-molecular FLPs are more affected compared to the inter-molecular FLPs.     

高中化学“物质转化及反应调控”项目式学习*——我是米酒酿造师

以“我是米酒酿造师——如何在家中酿造出美味可口的米酒”为项目主题,在化学、生物学科融合的大背景下,开展“物质转化及反应调控”的教学。通过“了解米酒酿造的原理、探究米酒酿造的影响因素、设计米酒酿造的方案”等3个核心活动,落实典型有机化合物的性质、有机化合物之间的转化等核心知识;在解决实际问题的过程中体会控制变量思想在科学探究中的重要作用,体会调控化学反应的速率和限度的重要意义。     

Experimental analysis and thermodynamic modelling of Nitroxynil solubility in pure solvent and binary solvent

Nitroxynil(NIT) is a commonly used anti-liver fluke drug for cattle and sheep, Its solubility is closely related to its preparation. In this work, the molar solubility of NIT in nine pure solvents (methanol, ethanol, 1,2-propanediolethyl, isopropanol, ethyl acetate, acetonitrile, n-butanol, phemethylol) and two kinds of binary mixtures with different ratio(ethanol + phemethylol; ethanol + acetonitrile) was determined by shake flask method over the temperature from 278.15 ～ 323.15 K at atmosphere pressure. Results show that the solubility of NIT in all tested solvents was increased with raised temperature. In mono-solvents, the mole fraction solubility of NIT was highest in phemethylol and the solubility order is: phemethylol > acetonitrile > ethyl acetate > methanol > n-butanol > ethanol > 1,2-propanediolethyl > isopropanol > water. In binary solvents, the mole fraction solubility increased with increasing ratio of phemethylol/acetonitrile. In mono-solvents, the modified Apelblat equation, λh equation, Van't Hoff model were applied to correlate the solubility data. In binary solvents, the modified Apelblat equation, λh equation, GSM model and Jouyban-Acree model were to correlate the solubility data. Solubility order of NIT in nine pure solvent and two binary solvent systems were analysed by using the Hansen solubility parameter (HSP). Activity coefficient was to access the solute–solvent molecular interactions. In addition, the dissolution of NIT is an endothermic and entropy-friendly process, since thermodynamic parameters such as enthalpy, entropy, and apparent standard Gibbs free energy are all greater than zero. The results will supply some essential data on recrystallization process, purification and formulation development of NIT in pharmaceutical applications.     

DMSO作为新的合成子在有机合成中的应用研究进展

二甲亚砜(DMSO)不但可以作为有机溶剂,同时还可以作为反应试剂,在有机合成中得到了广泛的应用.由于其具有来源广、价格低廉、操作简单等优点,近年来将DMSO作为反应试剂应用于有机合成反应引起了广大化学家的关注.本文作者对近几年来DMSO作为合成子在有机合成中的应用按照引入官能团的种类进行了总结,详细阐述了其转化为甲磺酰基、甲酰基、氰基、甲硫基等官能团的方法学研究,以期为开发DMSO新的应用提供参考依据.     

自然光照下PEG/PAA凝胶在Fe~(3+)/CA溶液中的凝胶-溶胶转化行为

将PEG/PAA凝胶浸入铁/柠檬酸(Fe3+/CA)溶液中,自然光照一定时间可实现凝胶-溶胶的相互转化,而且转化行为受溶液的组成及其p H影响。只有当溶液中[Fe3+]0∶[CA]0≤1∶2,且溶液的p H在1~6之间,该转化才会发生,通过改变溶液中[Fe3+]0∶[CA]0的值或溶液的p H可以有效地控制其转化速率。此外,结果还表明,当凝胶转化为溶胶后,向其中加入高价金属阳离子,例如Fe3+、Al3+、Ce4+、Cu2+等,溶胶又会再次转化为凝胶。由于这种新颖的特性,该凝胶有望应用于药物释放、细胞培养等领域。     

Printable Bioelectronics To Investigate Functional Biological Interfaces

Thin‐film transistors can be used as high‐performance bioelectronic devices to accomplish tasks such as sensing or controlling the release of biological species as well as transducing the electrical activity of cells or even organs, such as the brain. Organic, graphene, or zinc oxide are used as convenient printable semiconducting layers and can lead to high‐performance low‐cost bioelectronic sensing devices that are potentially very useful for point‐of‐care applications. Among others, electrolyte‐gated transistors are of interest as they can be operated as capacitance‐modulated devices, because of the high capacitance of their charge double layers. Specifically, it is the capacitance of the biolayer, being lowest in a series of capacitors, which controls the output current of the device. Such an occurrence allows for extremely high sensitivity towards very weak interactions. All the aspects governing these processes are reviewed here.     

Solubility of tridecanedioic acid in pure solvent systems: An experimental and computational study

Solubility has been extensively investigated by the phase equilibria approach at the mesoscale level, but its origin on the molecular and electronic levels is poorly understood. This study explored the solubility behaviour of crystalline solid in selected pure solvents with various functional groups by using both phase equilibria and molecular modelling methods. The model compound tridecanedioic acid (TDDA) solubility in methanol, ethanol, acetic acid, acetone, and ethyl acetate was determined from T = (283.15 to 323.15) K by a static method. It was found that almost all solutions studied exhibit non-ideal behaviour and deviate positively from Raoult’s law indicating the important role of homo-molecules interactions. Thermodynamic analyses of solution suggest that both enthalpy and entropy of solution govern the dissolution process. Computational studies on solubility behaviour were performed by using both density functional theory (DFT) calculations and molecular dynamic (MD) simulations. The results conclude that the (solute + solvent) interaction is not the only factor determining solubility, and (solvent + solvent) interaction also plays an important role. The simulated results are found to be qualitatively consistent with experimental values. Finally, solubility values were correlated by the empirically modified Apelblat equation and two local composition models of Wilson and NRTL.     

Experimental and theoretical study of thermodynamic properties of levoglucosan

The heat capacity of levoglucosan was measured over the temperature range (5 to 370) K by adiabatic calorimetry. The temperatures and enthalpies of a solid-phase transition and fusion for the compound were found by DSC. The obtained results allowed us to calculate thermodynamic properties of crystalline levoglucosan in the temperature range (0 to 384) K. The enthalpy of sublimation for the low-temperature crystal phase was found from the temperature-dependent saturated vapor pressures determined by the Knudsen effusion method. The thermodynamic properties of gaseous levoglucosan were calculated by methods of statistical thermodynamics using the molecular parameters from quantum chemical calculations. The enthalpy of formation of the crystalline compound was found from the experiments in a combustion calorimeter. The gas-phase enthalpy of formation was also obtained at the G4 level of theory. The thermodynamic analysis of equilibria of levoglucosan formation from cellulose, starch, and glucose was conducted.     

Thermodynamics of nanoadsorption from solution: Theoretical and experimental research

In this study, the effect of nanoparticle size on adsorption thermodynamics was investigated. The results of theoretical and experimental studies show that particle size significantly affects the equilibrium constant and thermodynamic properties of nanoadsorption. Relationships between the equilibrium constant, thermodynamic properties and particle size were derived using the thermodynamic theory of nanoadsorption. The equilibrium constant and thermodynamic properties were obtained by investigating the adsorption of Cu²⁺ onto different sizes of nano-ZnO and the adsorption of Ag⁺ onto different sizes of nano-TiO₂. Good agreement was achieved between results obtained by experiments and predicted by theoretical analyses. The equilibrium constant and the molar Gibbs free energy of nanoadsorption were found to increase with smaller nanoparticle size. However, the effects of particle size on the molar enthalpy and the molar entropy are uncertain. In addition, the molar Gibbs free energy, the molar enthalpy, the molar entropy and the logarithm of the equilibrium constant are linearly related to the reciprocal of the diameter of the nanoparticle. The thermodynamic properties revealed in this study may provide important guidelines for research and application in the field of nanoadsorption.