Viscosimetric Study of Some Cyclic Ethers with Benzene, Toluene, or Halobenzene

Experimental viscosities and the corresponding viscosity deviations for the binary mixtures of a cyclic ether (tetrahydrofuran, tetrahydropyran, 2-methyltetrahydrofuran, or 2,5-dimethyltetrahydrofuran) with benzene, toluene, fluorobenzene, or chlorobenzene are given at 25°C. The kinematic viscosities and the corresponding densities were measured with an uncertainty of ±10^{– 4} mm²-s^{– 1} and ±(5×10^{– 3}) kg-m^{– 3}, respectively. The viscosity data were correlated by the equations of Grunberg–Nissan, McAllister, and Heric. On the other hand, the results have been compared to the predictions, by the method proposed by Asfour.     

Excess Molar Enthalpies of Cyclic Ethers with Cyclohexane, Methylcyclohexane, or Chlorocyclohexane

Excess molar enthalpies for mixtures of tetrahydrofuran, tetrahydropyran, 2-methyltetrahydrofuran or 2,5-dimethyltetrahydrofuran with cyclohexane, methylcyclohexane, or chlorocyclohexane were determined at 25°C. The excess enthalpies are positive for the mixtures containing cyclohexane or methylcyclohexane, but negative for the mixtures containing chlorocyclohexane. The results were used with the Prigogine–Flory–Patterson theory to predict the corresponding excess molar volumes.     

Effects of the Presence of Cyclohexane or Methylcyclohexane on the Densities and Volumetric Properties of the Mixture (Benzene + Propionitrile)

Excess molar volumes, V_m^E, have been obtained as a function of composition for ternary-pseudobinary mixtures of [(benzene + cyclohexane or methylcyclohexane) + (propionitrile + cyclohexane or methylcyclohexane)] from the densities measured by means of a vibrating-tube densimeter at atmospheric pressure and a temperature of 298.15 K. The values of V_m^E have been correlated using the Redlich–Kister equation to estimate the coefficients and standard errors. The experimental and calculated quantities are used to discuss the mixing behavior of the components. The results show that the third component, cyclohexane or methylcyclohexane, has a significant effect on the interaction between benzene and propionitrile.     

Volumetric Properties of Ternary-Pseudobinary Mixtures Containing Benzene and Cyclohexane

Densities have been measured as a function of composition for ternary-pseudobinary mixtures of [(benzene + toluene or methylcyclohexane) + (cyclohexane + toluene or methylcyclohexane)] by means of a vibrating-tube densimeter at atmospheric pressure and the temperature 298.15 K. The excess molar volumes, V_m^E, were calculated from the densities and correlated using the Redlich–Kister equation to estimate the coefficients and standard errors. The experimental and calculated quantities are used to discuss the mixing behavior of the components. The results show the third component, toluene and methylcyclohexane, influences the interaction between benzene and cyclohexane.     

Sulfamic Acid as a Cost-effective Catalyst for Acetolysis of Cyclic Ethers

Sulfamic acid has been used as an efficient catalyst and green alternative for conventional acidic materials to promote the acetolysis reaction of THF to produce 1,4-diacetoxybutane. This method is also applicable in the acetolysis of other cyclic ethers, such as methyl substituted THF and tetrahydropyran and 1,4-dioxane which is less reactivity.     

Catalytic Reduction of Cyclic Ethers with Hydrosilanes

Catalytic reductive transformations of ethers as a synthetic building block are an important class of chemical reactions because a range of essential chemical feedstocks and fuels in contemporary life can be prepared through the key step of ethereal C?O bond cleavage of cellulosic biomass. Although conventional stoichiometric and catalytic methods for sp²‐ and sp³‐C?O bond cleavage of linear ethers and alcohols with hydrosilanes are well established, silylative ring opening of cyclic ethers has been less highlighted in this context. This review outlines catalytic systems for the silylative reduction of a range of cyclic ethers, including epoxides and sugars, leading to the corresponding alcohols and/or hydrocarbons. The chemical reactivity and selectivity of these ring‐opening catalytic processes are discussed with respect to the type of substrates; the representative catalytic working modes are also described.     

氧乙烯数对辛基苯酚聚氧乙烯醚表面扩张粘弹性质的影响

研究了非离子表面活性剂辛基苯酚聚氧乙烯醚TX-100、TX-102和TX-165(平均氧乙烯数依次为10、12、16)水溶液的表面扩张粘弹性质, 考察了氧乙烯数变化对表面吸附膜特性的影响. 研究结果表明, 随着氧乙烯数的增大, 表面膜表现出较大的模量和较强的弹性. 这是由于较长氧乙烯链在表面上的“平躺”产生较慢的弛豫过程造成的.     

Prediction of Excess Volumes and Excess Surface Tensions from Experimental Refractive Indices

Abstract

Refractive indices for the binary liquid mixtures: {hexane or heptane + ethanol}, {o-xylene + benzene} and {cyclohexane + benzene, toluene or hexane} were measured at 298.15 K. Excess refractive indices were calculated and fitted to a Redlich-Kister function. Using some mixture rules (Lorentz-Lorenz, Dale -Gladstone, Eykman, Oster, Arago-Biot and Newton), predictions for v^E have been made and compared with experimental data taken from the literature. Furthermore the Sugden equation has been used in two different ways for predicting excess surface tensions: the first one starting from densities and the other one from refractive indices. Results are plotted together with the literature data.     

苯并硫杂冠醚的质谱研究

报道了两个苯并硫杂冠醚的电子电离质谱，利用高分辩质谱（ＨＲＭＳ）和碰撞活化－质量分析动能谱（ＣＡＤ－ＭＩＫＥ谱）研究了它们的离子碎裂途径。苯并硫杂冠醚含两个硫原子的碎片离子进一步断裂时以丢失Ｃ２Ｈ４Ｓ为特征。     

环醚聚合化学与进展

本文综述了三元、四元及五元环醚单体的开环聚合机理(包括正、负离子及配位聚合)以及聚醚与共聚醚的制备与应用。     

Kinetic Study of the Oxidation of Catechols in the Presence of Some Aza‐crown Ethers by Digital Simulation of Cyclic Voltammograms

The electrochemical oxidation of catechols ( 1 ) have been studied in the presence of diaza‐18‐crown‐6 (DA18C6) ( 3a ), diaza‐15‐crown‐5 (DA15C5) ( 3b ), and aza‐15‐crown‐5 (A15C5) ( 3c ) as nucleophiles in aqueous solution, by means of cyclic voltammetry and controlled‐potential coulometry. The results indicate the participation of electrochemically generated o‐benzoquinones ( 2 ) in Michael‐type reaction with aza‐crown ethers ( 3 ) to form the corresponding new o‐benzoquinone‐aza‐crown ether adducts ( 5 ). Based on ECE mechanism, the observed homogeneous rate constants (k_obs) of the reaction of o‐bezoquinones ( 2 ) with aza‐crown ethers ( 3 ) were estimated by comparing the experimental cyclic voltammograms with the digital simulated results. The calculated observed homogeneous rate constants (k_obs) was found to vary in the order DA18C6>DA15C5>A15C5.     

Discovery of Novel Cyclic Ethers with Synergistic Antiplasmodial Activity in Combination with Valinomycin

With drug resistance threatening our first line antimalarial treatments, novel chemotherapeutics need to be developed. Ionophores have garnered interest as novel antimalarials due to their theorized ability to target unique systems found in the Plasmodium-infected erythrocyte. In this study, during the bioassay-guided fractionation of the crude extract of Streptomyces strain PR3, a group of cyclodepsipeptides, including valinomycin, and a novel class of cyclic ethers were identified and elucidated. Further study revealed that the ethers were cyclic polypropylene glycol (cPPG) oligomers that had leached into the bacterial culture from an extraction resin. Molecular dynamics analysis suggests that these ethers are able to bind cations such as K⁺, NH₄⁺ and Na⁺. Combination studies using the fixed ratio isobologram method revealed that the cPPGs synergistically improved the antiplasmodial activity of valinomycin and reduced its cytotoxicity in vitro. The IC₅₀ of valinomycin against P. falciparum NF54 improved by 4–5-fold when valinomycin was combined with the cPPGs. Precisely, it was improved from 3.75 ± 0.77 ng/mL to 0.90 ± 0.2 ng/mL and 0.75 ± 0.08 ng/mL when dosed in the fixed ratios of 3:2 and 2:3 of valinomycin to cPPGs, respectively. Each fixed ratio combination displayed cytotoxicity (IC₅₀) against the Chinese Hamster Ovary cell line of 57–65 µg/mL, which was lower than that of valinomycin (12.4 µg/mL). These results indicate that combinations with these novel ethers may be useful in repurposing valinomycin into a suitable and effective antimalarial.     

一些含钒杂多化合物的合成、表征及其在环己烷催化氧化反应中性能的比较

合成了一系列钒取代在不同位置的杂多化合物, 考察了它们在环己烷催化氧化反应中的活性及其过氧化氢的分解情况, 发现钒的配位环境是影响反应活性的重要因素. 其中以H₄PMo₁₁VO₄₀为代表的钒在配位原子位置上的磷钼钒酸, 不但显示了很好的催化环己烷氧化反应的活性, 而且H₂O₂的分解反应同时也得到了较好的抑制.     

一些含钒杂多化合物的合成、表征及其在环己烷催化氧化反应中性能的比较

合成了一系列钒取代在不同位置的杂多化合物, 考察了它们在环己烷催化氧化反应中的活性及其过氧化氢的分解情况, 发现钒的配位环境是影响反应活性的重要因素. 其中以H₄PMo₁₁VO₄₀为代表的钒在配位原子位置上的磷钼钒酸, 不但显示了很好的催化环己烷氧化反应的活性, 而且H₂O₂的分解反应同时也得到了较好的抑制.     

Oxidative Kinetic Resolution of Cyclic Benzylic Ethers

A manganese‐catalyzed oxidative kinetic resolution of cyclic benzylic ethers through asymmetric C(sp³)?H oxidation is reported. The practical approach is applicable to a wide range of 1,3‐dihydroisobenzofurans bearing diverse functional groups and substituent patterns at the α position with extremely efficient enantiodiscrimination. The generality of the strategy was further demonstrated by efficient oxidative kinetic resolution of another type of five‐membered cyclic benzylic ether, 2,3‐dihydrobenzofurans, and six‐membered 6H‐benzo[c]chromenes. Direct late‐stage oxidative kinetic resolution of bioactive molecules that are otherwise difficult to access was further explored.     

Electrochemical Study of the Micellization of Hexadecylpyridinium Bromide in the Presence of Some Crown Ethers

A membrane electrode selective to hexadecylpyridinium bromide was used to study the micellization of the surfactant in the presence of varying concentrations of crown ethers 15-crown-5, dicyclohexyl-18-crown-6 and dicyclohexyl-24-crown-8 at 27°C. The critical micelle concentration of surfactant was largely influenced by the crown ethers used, indicating their participation in the structure of the resulting micelle. The degree of attachment of crown ethers to the surfactant in the micellar structure was found to be 1. An estimation of the K_f for the 1:1 surfactant-crown interaction in the micellar region is reported. The degree of counter ion dissociation was found to increase with the crown ether concentration, and with the nature of macrocyclic ligands in the order 15-crown-5 < dicyclohexyl- l8-crown-6 < dicyclohexyl-24-crown-8. There was also some evidences for a rather strong interaction between dicyclohexyl-24-crown-8 and the surfactant in the submicellar concentration ranges in solution.     

Volumetric and acoustic properties of the ternary system (1-butanol+1,4-dioxane+cyclohexane)

Densities and speeds of sound for the ternary system 1-butanol+1,4-dioxane+cyclohexane have been measured at the temperatures of 298.15 and 313.15 K. Excess molar volumes and excess isentropic compressibilities have been calculated from experimental data and fitted by the Redlich-Kister equation for ternary mixtures. The ERAS model has been used to calculate excess molar volumes of the ternary mixture from parameters obtained from the constituent binary mixtures.     

聚氧乙烯醚类表面活性剂表面扩张粘弹性质研究

研究了非离子表面活性剂壬基苯酚聚氧乙烯醚NP-8, NP-10和NP-12水溶液的表面扩张粘弹性质, 考察了氧乙烯数的变化对表面吸附膜特性的影响. 研究结果表明, 三种表面活性剂的扩张弹性随着工作频率的增大而增大, 扩张粘性则在0.1~0.01 Hz范围内通过不明显的极大值; 扩张弹性和粘性随着浓度的增加在同一浓度处通过一个极大值; 氧乙烯数从8增加到12, 表面扩张弹性、粘性和相角的变化不大. 从发生在表面上和表面附近的微观弛豫过程的角度对实验结果进行了讨论.     

Isobaric Vapour-Liquid Equilibrium of Some Cyclic Ethers with Bromobenzene at Several Pressures

A dynamic recirculating still was employed to study the isobaric vapour-liquid equilibrium (VLE) at 40.0 and 101.3 kPa for the binary systems tetrahydrofuran, tetrahydropyran, 2-methyl-tetrahydrofuran and 2,5-dimethyl-tetrahydrofuran with bromobenzene. The experimental data were tested for thermodynamic consistency and correlated with the Wilson, NRTL and UNIQUAC equations. Predictions with the UNIFAC method were also obtained.