Influence of Temperature on Liquid–Liquid Equilibrium of Methanol + Toluene + Hexane Ternary Systems at Atmospheric Pressure

Phase equilibria of methanol?+?toluene?+?hexane ternary systems at (278.15, 283.15, 288.15 and 293.15) K at atmospheric pressure were investigated. The influence of temperature on the liquid–liquid equilibrium is discussed. All chemicals were quantified using gas chromatograph with a thermal conductivity detector coupled to a ChemStation and nitrogen as gas carrier, their mass fractions were higher than 0.999. From literature are found two articles from the same system at different temperatures studied here. Experimental data are compared with literature values. Values calculated using the NRTL and UNIQUAC equations are compared with the experimental data and it is found that the UNIQUAC equation fitted the experimental data better than the NRTL model for this ternary system.     

Stereodynamics of the Ca + HCl → CaCl + H molecular reaction imposed by the rotational-excited states of HCl

The effects of the initial rotational-excited states of the HCl molecule on the stereodynamics properties of the Ca + HCl molecular reaction are investigated using the quasiclassical trajectory theory and the analytical potential energy surface. The orientation and alignment behaviors for the rotational angular momentum of the product, along with the generalized differential cross section (PDDCS)-dependent polarization, are calculated to explore the stereodynamics properties. The initial rotational-excited states of the HCl molecule impose a remarkable effect on the vector correlation distributions, regardless of the orientation, alignment, or PDDCS. The forward, backward, and weak sideway scatterings are found in the Ca + HCl → CaCl + H molecular reaction. The results demonstrate that the initial rotational-excited state of j = 3 results in more obvious stereodynamics effects.     

Critical Behavior of {DMA + AOT + Octane} Nonaqueous Microemulsions with Various Molar Ratios of DMA to AOT

The coexistence curves of two nonaqueous microemulsions systems of {dimethylacetamide (DMA) + sodium di(2-ethyl-1-hexyl)sulphosuccinate (AOT) + n-octane}, with the molar ratios ω=(3.06 and 3.86) of DMA to AOT, were determined by precisely measuring the refractive index at constant pressure at temperatures within about 7 K of the critical temperature T _c. The critical exponents β and critical amplitudes B have been deduced from the coexistence curves. It was found that the values of β for both systems are inconsistent with the expected 3D-Ising value but approach the Fisher-normalization value of 0.365 over a rather wide temperature range. By increasing the molar ratio ω, the critical temperature T _c increases, but the critical (volume fraction) composition φ _c decreases, which is different from the trends observed for aqueous microemulsions.     

Ternary liquid–liquid equilibria for mixtures of (ethanol + toluene + n -decane)

The data on the liquid–liquid equilibrium in (ethanol?+?toluene?+?n-decane) have been measured at three temperatures 298.15, 303.15 and 313.15?K and ambient pressure. Gas liquid chromatography has been employed, to determine the composition of the substances in liquid phases. The measured tie-line data are presented. The experimental ternary liquid–liquid equilibrium data have been correlated, using the universal quasi chemical (UNIQUAC) and non-random tow-liquid (NRTL) activity coefficient models to obtain the binary interaction parameters of these components. Both the UNIQUAC and NRTL models, satisfactorily predict the equilibrium compositions. The partition coefficients and the selectivity factor of the toluene extraction from n-decane mixtures were calculated and presented.     

Liquid–liquid phase diagrams of H2O + 2-butanol + potassium phosphate and H2O + 2-butanol + Na2CO3 systems at 298.15 K

The phase diagrams for the ternary systems H₂O?+?2-butanol?+?K₂HPO₄/KH₂PO₄ (pH?=?7) and H₂O?+?2-butanol?+?Na₂CO₃ at 298.15?K were determined. Experimental binodals and tie lines for these systems are presented. The experimental results were correlated using an improved regular solution theory. The agreement between the correlation and experimental data is good.     

Experimental Study of Vapor–Liquid Equilibrium Data for Acetone + Methanol + 1-Methyl-3-octylimidazolium Thiocyanate

An experimental study on the isobaric vapor–liquid equilibria for the ternary system of acetone?+?methanol?+?1-methyl-3-octylimidazolium thiocyanate ([Omim][SCN]) as well as the two acetone?+?ionic liquid (IL) and methanol?+?IL binary systems was performed at 100 kPa using a recirculating still (VLE 602 Fischer apparatus). A low IL mole fraction of 0.027 was found to be sufficient break the azeotrope due to the high and specific interactions with acetone and methanol. The nonrandom two-liquid model was used to represent the experimental data. The results are compared with those in the literature for the same mixed solvent system using other ILs.     

Physical properties of the ternary mixture ethanol + water + 1-hexyl-3-methylimidazolium chloride at 298.15 K

In this work, densities and refractive indices of the ternary mixture ethanol?+?water?+?1-hexyl-3-methylimidazolium chloride ([C₆mim][Cl]) and of the binary systems containing the ionic liquids (ILs) have been measured at 298.15?K and atmospheric pressure. Excess molar volumes and changes of refractive indices on mixing were determined from experimental data. The binary data were correlated with the Redlich–Kister equation, while the Cibulka equation was applied for the ternary system.     

Synthesis of N-heterocycles via [4 + 3] cycloaddition of azomethine imine

Di, tri and tetra-nitrogen containing 7-membered heterocycles are the key building blocks for natural and medicinally active compounds. They are using as antidepressants, antiulcer, antibiotics, antiemetic and also used as herbicides and insecticides. These building blocks can be synthesized easily from [4 + 3] cycloadditon reaction of azomethine imine with the other suitable reacting partner. Research on this area is very much important as this area is not much explored till now. Hence, the synthetic literature survey towards the di-nitrogen containing heterocycles is paramount importance. Herein, we report numerous synthetic routes (metal catalyzed, metal free, asymmetric) of di-nitrogen containing 7-membered heterocycle through [4 + 3] cycloadditon reaction of the last 10 years (2011-2019).     

Peculiarities of Si and SiO2 Etching Kinetics in HBr + Cl2 + O2 Inductively Coupled Plasma

Plasma Chemistry and Plasma Processing - Peculiarities of the etching kinetics and mechanisms for Si and SiO2 in the HBr?+?Cl2?+?O2 inductively coupled plasma were...     

Viscometric and volumetric properties of benzene + methyl acetate,or + methyl propanoate,or + methyl butanoate binary systems at 283.15, 298.15 and 313.15 K

Viscosities and densities of three binary liquid mixtures, benzene?+?methyl acetate, benzene?+?methyl propanoate and benzene?+?methyl butanoate, have been measured at 283.15, 298.15 and 313.15?K, and atmospheric pressure. From experimental data, viscosity deviation, excess energy of activation for viscous flow, and excess molar volume were calculated and satisfactorily correlated with Redlich and Kister equation. Empirical and semiempirical equations and the predicted group-contribution method, universal automatic computer, were applied.     

Isobaric Vapor–Liquid Equilibrium Data for the Quaternary System of sec-Butyl Acetate + sec-Butyl Alcohol + Dimethyl Sulfoxide + 1-Ethyl-3-methylimidazolium Acetate at 101.3 kPa

Journal of Solution Chemistry - The isobaric vapor–liquid equilibrium (VLE) data for the quaternary system sec-butyl acetate (SBAC)?+?sec-butyl alcohol...     

Short Chain Branches Distribution Characterization of Ethylene/1-Hexene Copolymers by Using TREF + 13C-NMR and TREF + SC Methods

Summary: Short chain branches distribution (SCBD) is the key factor for high density polyethylene (HDPE) pipe materials to achieve their excellent performance for long term (50 years) applications. However, the precise SCBD characterization of these HDPE materials with relatively low content of comonomer incorporation still remained as a challenge in this field. In this work, two characterization methods, namely temperature rising elution fractionation (TREF) cross step crystallization (SC) (TREF + SC) and TREF cross ¹³C-NMR (TREF + ¹³C-NMR), have been respectively used to qualitatively and quantitatively investigate the SCBD for two HDPE pipe materials (PE-1 and PE-2 with different long term performances) with small amount of 1-hexene incorporation prepared from SiO₂-supported silyl chromate catalyst system (S-2 catalyst) during UNIPOL gas phase polymerization. The comparison of SCBD between the two samples showed that: although short chain branches of PE-2 with good performance were less than those of PE-1 with bad performance, PE-2 showed less comonomer incorporation on the low crystallinity and low molecular weight (MW) fractions keeping even higher comonomer incorporation on the high crystallinity and high MW parts compared with PE-1. This difference on the SCBD for PE-1 and PE-2 was thought to be the key factor which is responsible for their great difference on environment slow crack resistance (ESCR). Moreover, TREF + SC method further reflected the intra- and inter-molecular heterogeneities of each fraction from the two HDPE samples through the lamella thickness distribution compared with TREF + ¹³C-NMR.     

Collaborative control of branching ratio in the O + HO2 → OH + O2 reaction via vibrational and rotational excitation

To understand the effect of different vibrational and rotational modes of reactant to enhance the reactivity of the O + HO₂ → OH + O₂ reaction, we revisited this important atmospheric reaction. We report here a quasi-classical trajectory (QCT) study of the reaction dynamics on a recently developed full-dimensional potential energy surface (PES). Our previous work has indicated that this reaction has two pathways, the H abstraction (HA) channel and the O abstraction (OA) channel, which lead to totally different product energy distribution. In this work, we identified that the vibrational excitation of the OH stretching (v₁) mode of HO₂ is the switch of the HA channel at low collision energy; meanwhile, the rotational excitation can also greatly change the branching ratio of the two pathways. With the excitation of v₁ mode, the original negligible HA channel controlled by the tight transition state becomes quite important. This work presents an approach to control the branching ratio via collaboration between vibrational and rotational excitation and will enrich the knowledge of the O + HO₂ reaction in atmospheric chemistry and physics.     

Solvation Behaviors of Poly(acrylic acid) in Mixed Solvents of 2-Butoxyethanol + Water

Poly(acrylic acid) (PAA) is a well known weak polyelectrolyte in water but little is known about the solvation behavior of PAA in the mixtures of alcohol?+?water. In this study, the solvation behavior of PAA in the mixed solvents composed of 2-butoxyethanol (2BE)?+?water were investigated by measurements of volumetric properties, electrical conductivity, resonance light scattering and dynamic light scattering. All the measured experimental properties showed extrema or abrupt changes at a 2BE mole fraction of about 0.017 in 2BE?+?water. This may be explained by the formation of aggregates of 2BE and water, which is a poor solvent for PAA and results in cononsolvency of PAA in the mixture of the two good solvents, 2BE and water. We found that the volumetric property is sensitive to the occurrence of the specific aggregate of 2BE and water and the interactions in the complex fluid mixtures.     

WDX Analysis of Rapidly Quenched Nd-Fe-B Alloys with Ti + C Additives

 Quenched stoichiometric Nd-Fe-B alloys with Ti + C additives, which improve the hard magnetic properties, were investigated by EPMA technique. The exact quantitative wavelength dispersive analysis meets with two problems: the carbon blank value and the C-Kα line coincidence with Nd-Mγ, Nd-Mα and Nd-Mζ of higher diffraction orders. The carbon blank value depends on the special residual gas pressure in the recipient and was determined by repeated measurements of a carbon free iron reference specimen e.g. with subsequent corrections of the carbon content. The second problem can be solved by blanking out the Nd induced contribution to the C-Kα region by a differential detection mode. In this case an energy discriminator was used to set a lower and an upper level in order to suppress the neighbouring coincident lines. The optimized analysis allowed an exact determination of carbon content in all investigated phases.     

Thermodynamics of binary mixtures with strongly negative deviations from Raoult's Law. X. linear alkanoate + CHCl3 or + 1,1,2,2-tetrachloroethane

Mixtures formed by linear alkanoates and CHCl₃ or 1,1,2,2-tetrachloroethane, which show strongly negative deviations from the Raoult's law, have been studied in the framework of the dispersive–quasichemical (DISQUAC) model. Systems involving CH₂Cl₂; CCl₄, Cl₃C–CH₃ or ClCH₂–CH₂Cl have also been briefly considered in order to carry out a more complete study. The corresponding interaction parameters are reported. As in other previous applications, the first (Gibbs energy) and third (heat capacity) quasichemical interaction parameters do not depend on the mixture components. DISQUAC represents fairly well vapor–liquid equilibria, VLE, and molar excess enthalpies, H ^E, of the systems considered. VLE of the methyl ethanoate?+?CHCl₃?+?benzene mixture is also well described by the model neglecting ternary interactions. UNIFAC (universal functional activity coefficient) fails when representing H ^E of systems containing very long alkanoates. The mixture structure is investigated using the concentration–concentration structure factor, S _CC(0). Heterocoordination is prevalent even at very high temperatures.     

Thermodynamics of Mixing and Solvation of Ibuprofen and Naproxen in Propylene Glycol + Water Cosolvent Mixtures

By using the van’t Hoff and Gibbs equations, solubility data of ibuprofen (IBP) and naproxen (NAP) determined at several temperatures in propylene glycol (PG) + water (W) cosolvent mixtures were used to evaluate the Gibbs energies, enthalpies, and entropies of solution, mixing and solvation. The solubilities are greater in pure PG and lower in W in both cases at all studied temperatures. These results clearly show that a cosolvent effect is present in these systems. The solvation of these drugs was greater in W compared to PG, and it was lower in the cosolvent mixtures compared with the pure solvents. By means of an enthalpy-entropy compensation analysis, non-linear ΔH _soln^o versus ΔG _soln^o compensation plots were obtained, with negative and positive slopes if all of the composition intervals are considered. Accordingly, it follows that at low PG solvent fractions the dominant factor for the solubility of IBP and NAP in this cosolvent system is the entropy, probably due to loosening of the water structure caused by the addition of the cosolvent.     

Study of equilibrium solution and thermodynamic models in correlation with solubility data of rivastigmine tartrate in (H2O + isopropanol), (H2O + ethanol), and (H2O + acetonitrile) binary solvent mixtures

Millions of people around the world have been suffering from Alzheimer’s disease (AD) everyday. Rivastigmine tartrate is a potential AD drug. A crystallization process can enhance purities of rivastigmine tartrate properly. Predictive models for solubilities of rivastigmine tartrate will improve subsequent industrial crystallization process design. In this work, the solubility of rivastigmine tartrate in (H₂O?+?isopropanol), (H₂O?+?ethanol), and (H₂O?+?acetonitrile) binary solvent systems in the temperature range of 278.15–333.15 K under atmospheric pressure was measured and investigated by employing the analytical stirred-flask method. Binary solvent systems of rivastigmine tartrate overcame drawbacks of mono-solvent crystallization systems, such as high viscosity. Three thermodynamic models, including modified Apelblat equation, the general cosolvency model, and the Jouyban–Acree model, were employed to correlate with the obtained experimental solubility data. Moreover, the calculations of apparent thermodynamic properties of rivastigmine tartrate dissolution process involving the Gibbs free energy, enthalpy, and entropy were accomplished by using the van’t Hoff analysis. Among the three models, the modified Apelblat equation is the most suitable one for predicting the solubility behavior of rivastigmine tartrate in binary solvent systems. Based on the data from modified Apelblat equation, a crystallization process of (H₂O?+?ethanol) binary solvent mixture was developed.