X-ray Structural Analysis of Liquid Solutions of n-Butanol-1 in Cyclohexane

Abstract

Angular distributions of intensity of X-ray radiation scattered in solutions of n-butanol-1 in cyclohexane have been measured and analyzed. The mean least intermolecular distances in the solution were determined. It was established that in the range of very low concentrations X of the solutions studied the distribution of the intermolecular distances R(X) revealed three extremes. In this concentration range the fluctuations of the distance R are related to the earlier observed fluctuations of the solution density: the minimum in R(X) at X?0.028 mole fraction corresponds to the maximum in d(X) in the range 0.015 ≤X≤ 0.035 mole fraction, while the two maxima in R(X) at X ?0.007 and X?0.05 mole fraction correspond to the minima in d(X) in the mole fraction ranges 0≤ X ≤0.015 and 0.026 ≤ X ≤0.05.

In the range 0.05 ≤X≤ 0.9 mole fraction the main role in ordering of the solution molecules is played by the associated molecules of the alcohol with voids containing individual molecules of the solvent.     

Ultrasonic study of binary aqueous mixtures of three common eutectic solvents

Ultrasonic velocities have been measured for different binary mixtures of common choline chloride-based deep eutectic solvents (DESs), namely, reline, glyceline and ethaline with water, in the range of temperature: 303.15–353.15 K. The experimental data measurements with different mole fractions of DES–water solutions were utilised in fitting four different models for speed of sound. These models correlate the speed of sound with some physical properties such as molar volumes, molar components sound velocity, densities, molecular weights, collision factors etc. A close match was obtained with these models with an average relative error of less than 4% for all data points used. It was observed that the ultrasonic velocity increases with the concentration of DES solvent and decreases with temperature. Moreover, this study roughly indicated that the intermolecular interactions in reline and ethaline aqueous mixtures exist in the form of disruption of dipole–dipole interactions (that varies considerably as a function of DES mixture composition and solution temperature). On the other hand, the interactions on the molecular level in glyceline aqueous solution are mainly due to dipole–dipole intermolecular forces.     

Thermodynamic properties of some concentrated polymer solutions

Solubilities of several solvents were measured in four molten polymers by using an isobaric vapor-pressure apparatus. Solvent concentration ranged from 0.5 to 15 wt-%. The systems polyisoprene–benzene and polyisobutylene–benzene were studied at 80.0°C; polyisobutylene–cyclohexane was studied at 100.0°C; ethylene–vinyl acetate copolymer (EVA)–cyclohexane, EVA–isooctane, and poly(vinyl acetate)–isooctane were studied at 110.0°C. Of six polymer–solvent systems studied, all except poly(vinyl acetate)–isooctane appear to exhibit hysteresis in a single sorption–desorption cycle starting with dry polymer. The desorption curves of solvent activity plotted versus solvent weight fraction show an inflection point, suggesting localized adsorption of solvent molecules. Experimental data were analyzed with a theory which takes into account adsorption of solvent by polymer in addition to differences in free volumes and intermolecular forces. The theory gives a semiquantitative representation of the experimental data.     

Studies on the internal structure of the binary mixtures of N,N-dimethylacetamide with 2-methoxyethanol, 2-ethoxyethanol, 2-propoxyethanol and 2-butoxyethanol by means of measuring their densities and relative permittivities at 298.15 K

ABSTRACT

The densities and relative permittivities of binary mixtures of N,N-dimethylacetamide with 2-methoxyethanol, 2-ethoxyethanol, 2-propoxyethanol and 2-butoxyethanol have been measured as a function of composition, at T = 298.15 K. From the experimental data the excess molar volume (V^E) from a mole fraction and the excess relative permittivity (ε^E) from a volume fraction average have been calculated. The results are discussed in terms of intermolecular interactions and structure of studied binary mixtures.     

Solvent effect on the inclusion of 2-acetylnaphthalene by 1,1-di(p-hydroxyphenyl)cyclohexane

The effect of the solvents acetone (AT), dimethylsulfoxide (DMSO) and methylcellosolve (MCS) on the inclusion of 2-acetylnaphthalene (2-AN) in the host, 1,1-di(p-hydroxyphenyl)cyclohexane (DHC) has been investigated. Each solvent molecule is included in DHC in a molar ratio of 1.0, when DHC is crystallized from the solvents. The evaporation rate of these solvents from the host lattice decreases in the order AT, MCS and DMSO. The order agrees well with the interaction strength between the host and solvent molecule, which was measured by DSC and IR. 2-AN cannot be included in the crystals by crystallization from MCS and DMSO solutions. However, in AT solution both AT and 2-AN are included competitively and the morphology of the crystals is different from that obtained in pure solution. The amount of 2-AN in the crystals increases continuously with its concentration in solution. This behavior indicates that AT is replaced by 2-AN and the solid solution of the molecular complex is formed. The solid solution is a metastable form and the solution-mediated tranformation to the stable form (which includes only AT) was observed.     

Model system for concentrated electrolyte solutions: Thermodynamic and transport properties of ethylammonium nitrate in acetonitrile and in water

Ethylammonium nitrate (ETAN), a low melting fused salt which is completely miscile in water and in many non-aqueous solvents, was used as a model system for the study of concentrated non-aqueous electrolyte solutions. Acetonitrile (AN) was chosen as a representative aprotic solvent. Some data were also obtained for water as solvent. The properties investigated over the whole mole fraction range, many as a function of temperature, were solid-liquid phase diagram, volume, heat capacity, conductivity and viscosity. Most properties in both solvents vary in a regular fashion over the whole mole fraction range and the properties at high concentration rapidly tend to those of the molten salt. The apparent volumes and heat capacities vary linearly with lnX₂ over a large mole fraction range. There is evidence of significant association in AN (K _A =1094 l-mol⁻) but not in water. The low concentration thermodynamic data were fitted with an association model using the above K _A to obtain the partial molar quantities of ETAN at infinite dilution and in the associated state. These latter values are of the same magnitude as the molar quantities of the molten electrolyte.     

Synthesis of reversible fluorescent organogel containing 2-(2′-hydroxyphenyl)benzoxazole: fluorescence enhancement upon gelation and detecting property for nerve gas simulant

A new low molecular mass organogelator 1 containing 2-(2′-hydroxyphenyl)benzoxazole (HPB) group with long alkyl chain was synthesized by the reaction with 5-amino-2-(2′-hydroxy-4′-methylphenyl)benzoxazole and dodecyl isocyanate in THF at room temperature. The reversible gelation ability of 1 was investigated using a heating-cooling method in various organic solvents. The stable organogel was formed from carbon tetrachloride or from cyclohexane at the concentration as low as 0.9%. The self-assembled supramolecular gel structure formed by non-covalent bonding was confirmed with field emission-scanning electron microscope (FE-SEM) exhibiting fibril- or ribbon-shaped structure depending on the solvent used. Regarding the aggregation-induced emission enhancement (AIEE) phenomenon, the optical properties were investigated in its solution and gelled state. The detecting properties of resulting organogel toward nerve gas simulant were monitored by UV-vis and fluorescence spectroscopy. Both color change from colorless to greenish yellow and disruption of gel structure resulting from alteration in intermolecular forces were observed upon the exposure to nerve gas simulant.     

Enthalpy characteristics of L-proline dissolution in certain water–organic mixtures at 298.15 K

A thermochemical study of the processes of L-proline dissolution in aqueous solutions of acetonitrile, 1,4-dioxane, acetone, dimethyl sulfoxide, nitromethane and tetrahydrofuran at Т = 298.15 K in the range of organic solvent concentrations x₂ = 0–0.25 mole fractions is performed. Standard values of the enthalpies of solution and transfer of L-proline from water to mixed solvent, and the enthalpy coefficients of pairwise interactions between L-proline and molecules of organic solvents, are calculated. The effect the composition of a water–organic mixture and the structure of organic solvents have on the enthalpy characteristics of L-proline dissolution and transfer is examined. The effect the energy properties of intermolecular interactions between components of a mixed solvent has on the intermolecular interactions between L-proline and molecules of cosolvent is estimated. The correlation between the enthalpy characteristics of L-proline dissolution and electron-donor properties of organic cosolvent in aqueous solutions is determined.     

Relationship between variously associated molecules in the HF-Et2CO solution

Data on the relationship between the molecules involved in various heteroassociates (HAs) and “free” molecules in the HF-Et₂CO binary liquid system (BLS) are obtained by two independent methods: experimental and computational. The first method is applicable in the 0:1–6:1 molar range provided that the IR spectrum of the solvent molecule contains a band whose frequency and intensity can be measured when this molecule passes from the “free state” to the composition of all Has present in BLS. The second method is based on taking into account the material balance between the “free” molecules and molecules involved in various HAs of the solvent and HF. This method requires the knowledge of stoichiometric ratios of molecules in HAs and concentrations at which they appear in the solution. It is shown that in HF-Et₂CO BLS, starting from the molar fraction of HF of ～0.25, the majority of molecules is involved in the composition of the complexes, and at the molar fraction of HF of ～0.50–0.92 already 90–100% of molecules of the solution form HAs.     

Solubility of Anthracene in Binary Carbon Tetrachloride + Alkane Solvent Mixtures

Abstract

Experimental solubilities are reported for anthracene in binary solvent mixtures containing carbon tetrachloride with n-hexane, n-heptane, n-octane, cyclohexane, methylcyclohexane and isooctane at 25°C. Results of these measurements, combined with the excess Gibbs free energies of the binary solvents, are used to test predictive expressions derived from the nearly ideal binary solvent (NIBS) model. Expressions based on a volume fraction average of solute properties in the two pure solvents predict anthracene solubilities to within a maximum deviation of 4.5% and an overall average deviation of 1.8%.     

Study of solvent effects on the stability constant and ionic mobility of the dibenzo‐18‐crown‐6 complex with potassium ion by affinity capillary electrophoresis

The effect of solvent on the strength of noncovalent interactions and ionic mobility of the dibenzo‐18‐crown‐6 complex with K⁺ in water/organic solvents was investigated by using affinity capillary electrophoresis. The proportion of organic solvent (methanol, ethanol, propan‐2‐ol, and acetonitrile) in the mixtures ranged from 0 to 100 vol.%. The stability constant, K_KL, and actual ionic mobility of the dibenzo‐18‐crown‐6‐K⁺ complex were determined by the nonlinear regression analysis of the dependence of the effective electrophoretic mobility of dibenzo‐18‐crown‐6 on the concentration of K⁺ (added as KCl) in the background electrolyte (25 mM lithium acetate, pH 5.5, in the above mixed hydro–organic solvents). Competitive interaction of the dibenzo‐18‐crown‐6 with Li⁺ was observed and quantified in mixtures containing more than 60 vol.% of the organic solvent. However, the stability constant of the dibenzo‐18‐crown‐6‐Li⁺ complex was in all cases lower than 0.5 % of K_KL. The log K_KL increased approximately linearly in the range 1.62–4.98 with the increasing molar fraction of organic solvent in the above mixed solvents and with similar slopes for all four organic solvents used in this study. The ionic mobilities of the dibenzo‐18‐crown‐6‐K⁺ complex were in the range (6.1–43.4) × 10^?9 m² V^?1 s^?1.     

Thermodynamic interactions and characterisation of naphthenic oil by inverse gas chromatography

The thermodynamic properties of naphthenic oil, a plasticiser, were investigated by means of inverse gas chromatography (IGC) using 10 different kinds of solvents as probes. Some thermodynamic parameters, such as specific retention volume, weight fraction activity coefficient, Flory–Huggins interaction parameter, partial molar heats of mixing and solubility parameter were obtained to judge the interactions between oil and solvents and the solubility of oil in these solvents. The results indicated that n-heptane, n-hexane, cyclohexane, chloroform, benzene and diethyl ether are good solvents for oil at experimental temperatures. The solubility parameters of oil varied from 13.94 to 13.21?(J?cm^?3)^1/2 at temperature range 323–353?K. The solubility parameter of oil was calculated to be 14.38?(J?cm^?3)^1/2 at room temperature, which is consistent with that obtained using surface tension–solubility parameter relation method.     

Density and relative permittivity of (pyridine + 2-methoxyethanol, 2-ethoxyethanol, 2-propoxyethanol,and 2-butoxyethanol) binary mixtures at 298.15 K

The densities and relative permittivities of binary mixtures of pyridine with 2-methoxyethanol, 2-ethoxyethanol, 2-propoxyethanol and 2-butoxyethanol have been measured as a function of composition, at T = 298.15 K. From the experimental data the excess molar volume (V^E) and the deviation in the relative permittivity (Δε) from a mole fraction average have been calculated. The results are discussed in terms of intermolecular interactions and structure of studied binary mixtures.     

Cobalt(II) octanoate and cobalt(II) perfluorooctanoate catalyzed atom transfer radical polymerization of styrene in toluene and fluorous media—A versatile route to catalyst recycling and oligomer formation

Cobalt(II) perfluorooctanoate‐catalyzed atom transfer radical polymerization (ATRP) and reverse ATRP were developed to prepare oligostyrenes (M_n < 2500) with low polydispersities M_w/M_n < 1.5. Fluorous biphase catalysis was applied for effective recycling of catalyst and fluorous solvent. The homogeneous polymerization reaction was performed at 90 °C in toluene/cyclohexane/perfluorodecalin mixture (1:1:1) and fluorine‐free solvents. Temperature‐induced phase separation of this fluorous solvent mixture occurred at room temperature and proved to be the key for the very effective separation of the cobalt(II) perfluorooctanoate from the oligostyrene and fluorine‐free solvents. Both the fluorine‐tagged cobalt catalysts and the fluorous media were recycled and reused up to three times without encountering catalyst activity losses. The roles of cobalt catalysts, fluorous media, and monomer/initiator ratio were examined with respect to the polymerization kinetics. Fluorine‐containing and fluorine‐free cobalt(II) octanoate catalyzed controlled styrene oligomerization according to the ATRP mechanism. The molar mass control range was limited in fluorous biphase catalysis most likely because of precipitation of high molar mass polystyrenes in the fluorous reaction medium. To the best of our knowledge, this is the first time temperature‐induced phase separation of fluorous and fluorine‐free solvents has been successfully applied to polymerization processing. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3804–3813, 2005     

Acoustical parameters of toluene + chloroform + cyclohexane mixtures at 303.15, 308.15, and 313.15 K

Ultrasonic velocity, density and viscosity of the ternary mixture of toluene + chloroform + cyclohexane, were measured at 303.15, 308.15, and 313.15 K. The thermodynamically parameters such as adiabatic compressibility (??), intermolecular free length (L _f), free volume (V _f), internal pressure (?? _i ), acoustic impedance (Z), molar sound velocity (R), and molar compressibility (W) have been obtained from the experimental data for all the mixtures, with a view to investigate the exact nature of molecular interaction. Adiabatic compressibility and intermolecular free length decrease with increase in concentration and temperature. The other parameters show almost increasing concentration of solutes. These parameters have been further used to interpret the molecular interaction part of the solute and solvent in the mixtures.     

Acoustical study on ternary mixture of dimethyl acetamide (DMAC) in diethyl ether and isobutyl methyl ketone at different frequencies

The experimental density (ρ) and the velocity (U) for ternary mixture of dimethyl acetamide diethyl ether and isobutyl methyl ketone at different frequencies (2, 4, 6 and 8 MH_Z) have been measured at a constant temperature of 308 K. These data have been used to compute acoustic impedance (Z), adiabatic compressibility (K _s), intermolecular free length (L_f ), molar volume (V_m ), molar sound velocity (R), molar compressibility (B), available volume (V _a), Lennard-Jones potential repulsive term exponent (n), relative association (R _A), interaction parameter (X) and excess values of some of the above parameters for entire range of mole fraction and are interpreted to explain molecular interaction occurring in the liquid mixture.     

The tautomerism of 5-chloro-2-hydroxypyridine. Comments on a paper by Srivastava and Prasad

Infrared and U.V. spectra are presented to show that 5-chloro-2-hydroxypyridine exists mainly in the pyridone form in solution in carbon tetrachloride, chloroform and cyclohexane, with extensive NH⋯OC intermolecular association at least in the former two solvents; in dioxane the pyridone and the pyridinol form are present in roughly equal amounts. As 2-pyridones are capable of forming centrosymmetric bimolecules of zero dipole moment, replacement of a highly polar solvent by a non-polar one does not necessarily displace the tautomeric equilibrium to predominance of the pyridinol tautomer, even though that has a much lower dipole moment than an individual 2-pyridone molecule. Some conclusions of Srivastava and Prasad's are questioned.     

Studies on Associated Solutions. Part II. Physicochemical Properties of Acetonitrile-Propan-2-ol Mixtures

Abstract

The ¹H-NMR spectra of liquid binary mixtures of acetonitrile and propan-2-ol, were recorded at 298 K over almost the whole range of the mixed solvent compositions. From these data were found the values of the spectral parameter, Δδ(ACN-PrOH-2). The densities (d ₁₂) and relative permittivities (?₁₂) of the mixed solvent were measured at 288.15K, 293.15K, 298.15K, 303.15K and 308.15K, as well as refractive indices at 298.15K. From all these data, the molar volumes (V _m), temperature coefficients of relative permittivities (α_n) and their deviations from ideality were calculated. Additionally, the Kirkwood's correlation factors (g _K) were found. The values of these properties are discussed in terms of interactions of acetonitrile with propan-2-ol.     

Tuning catalyst solubility in CO2 by changing molar volume

Abstract

Poor-solvating property of supercritical carbon dioxide (scCO₂) has been a great challenge, which limits the use of CO₂ as a common “green” solvent. The present report describes that by increasing molar volume (v) and lowering the melting temperature, which lowers cohesive energy density or solubility parameter (δ), it is possible to increase the solubility of metal-based catalysts in scCO₂ without using costly fluorinated or tailor-made CO₂-philic modifications. We have studied various chlorodistannoxanes (1) and Cu–β-diketonates (2) to support our views. The study of bio-diesel production and transesterification of hindered esters using 1 in scCO₂ shows a 2–8-folds rate enhancement coupled with an easier catalyst and product separation than that in organic solvents. The methodology, which works at least within the range of Van der Waals sphere of interactions, can be useful to solubilizing the molecules in scCO₂ and carries great opportunity in catalysis as well as in separation science.     

疏水作用对光化学和光物理过程的影响 Ⅶ.芘基烷基酮的荧光光谱及其在不良溶剂中的簇集

溶剂的极性对芘基烷基酮的单体荧光和激基缔合物荧光有很大影响,在非极性溶剂中单体荧光很弱,随着溶剂极性增大,单体荧光增强,单体荧光和激基缔合物荧光明显红移。利用芘基烷基酮荧光的这些性质研究了长链分子在二甲基亚砜-水(DMSO-H₂O)中的簇集现象。在浓度非常低的情况下,长链芘基烷基酮发射激基缔合物荧光,单体荧光也明显蓝移,表明芘基烷基酮形成了簇集体。长链饱和烷烃和芘基烷基酮发生共簇集,簇集体内的极性比环己烷的极性稍大。