Solvents Cyclohexane Research Articles

A reverse lyotropic liquid crystal formed by cetylpyridiniumchloride in cyclohexane with the assistance of aromatic counterions

The self-assembly of the cationic surfactant cetylpyridiniumchloride (CPC) in cyclohexane was studied using polarizing-microscopy (POM), small angle X-ray scattering (SAXS), and rheology measurements. Homogeneous solutions of CPC/aromatic salts were produced using aromatic salts, specifically, NaBzs, NaNphs, or NaSal. The majority of the samples showed highly viscous gel-like appearances. SAXS measurements together with POM observations indicate hexagonal liquid crystals in both the CPC/NaNphs and CPC/NaSal, while multiple types of aggregates were shown to co-exist in the CPC/NaBzs. These were attributed to the interactions of aromatic counterions with the pyridinium head-group of CPC, resulting in increased size of the CPC head to different extents depending on the aromatic counterions. The formation of core-shell aggregates consequently caused further packing into liquid crystals. The specific role of NaSal that carried an ortho-hydroxyl in its benzene ring is discussed, and the mechanism of trace water molecules bridging neighboring NaSal molecules was revealed according to Fourier transform infrared (FT-IR) measurements. The samples had high viscoelasticity, for example, the steady-state low-shear viscosity at a shear rate of 0.001, ηL, of the samples at W0 = 32 was 3.3 × 105, 2.0 × 104, and 6.8 × 102 Pa·s for CPC/NaBzs, CPC/NaNphs, and CPC/NaSal, respectively, at 25 °C. The corresponding elastic plateau moduli, G′P, were 1.9 × 103, 1.1 × 103, and 1.1 × 102 Pa, respectively. The temperature effect was examined for samples at W0 = 32, which were found to retain high viscosity at higher temperatures, for example, the relative viscosity to solvent cyclohexane, ηr, reached 107 and 105 for CPC/NaBzs and CPC/NaNphs, respectively, at 70 °C.

Harnessing solvent effects to integrate alkylamine into metal–organic frameworks for exceptionally high CO2 uptake

Alkylamine modified MOF prepared with a less polar solvent (cyclohexane) has a higher alkylamine loading amount and higher CO2 uptake than when prepared in a more polar solvent (dichloromethane).

Selective phenol hydrogenation under mild condition over Pd catalysts supported on Al2O3 and SiO2

Cyclohexanone (CHONE) is the key intermediate in the manufacture of nylon-6 and nylon-66. Selective hydrogenation of phenol into CHONE was investigated over Pd/SiO2 and Pd/Al2O3. The results show that the yield of CHONE reaches 98% or more over Pd/Al2O3 and Pd/SiO2 at 333 K under atmospheric pressure in cyclohexane solvent. High activity of Pd/Al2O3 is promoted by Lewis acidity, and phenol can be converted 100% within 300 min. The hydrogenation of CHONE occurs until the conversion of phenol approaches completion. Pd/SiO2 with smaller Pd nano-particles presents higher selectivity. For polar solvent, such as ethanol and dichloromethane, the activity of Pd catalysts decreases greatly. Auxiliary experiments verify that phenol adsorbs on Pd catalysts via the formation of π–c with an aromatic ring. Increased hydrogen pressure not only promotes significantly the rates of hydrogenation, but also increases the selectivity for CHONE, especially over Pd/SiO2-1 catalyst.

Solubility Measurement and Thermodynamic Properties of Levetiracetam in Pure and Mixed Solvents

In this work, the solid–liquid equilibrium for levetiracetam in 10 neat solvents (methanol, ethanol, n-propanol, isopropanol, acetone, acetonitrile, ethyl acetate, 1,4-dioxane, toluene, and cyclohexane) and binary liquid mixtures (ethanol + ethyl acetate) was measured by using a static gravimetric method at temperatures T = 283.15–323.15 K under pressure of 101.2 kPa. In general, the equilibrium solubility was highest in methanol and lowest in cyclohexane. The modified Apelblat equation, λh equation, Wilson model, and NRTL model were used to correlate the solubility data in monosolvents; and the Jouyban–Acree model, van’t Hoff–Jouyban–Acree model, and Apelblat–Jouyban–Acree model were used to correlate the experiment data in the binary solvent mixtures. Compared with the results of the above models, the calculated solubility provided good results with the experimental data. Consequently, for the monosolvents, the values of root-mean-square deviation and relative average deviation were not exceeding 9.91 ×...

Sodium Salicylate: An In-Depth Thermal and Photophysical Study.

Sodium salicylate (2-hydroxybenzoate) has been fully characterised by single-crystal X-ray diffraction (SCXRD), thermogravimetric analysis in combination with in operando FTIR spectroscopy and GC-MS, as well as by UV/Vis absorption and photoluminescence spectroscopy backed up by DFT calculations. SCXRD revealed a layered crystal structure composed of ionic sheets formed by Na+ -O contacts sandwiched between π-stacked aromatic rings of the salicylate anion oriented perpendicular to the layer plane. Only weak van der Waals interactions hold the individual sheets together. No solid/solid or solid/liquid phase transitions were observed upon heating, but a three-step decomposition was observed, with the first onset at 245 °C corresponding to concomitant release of CO2 and phenol. The UV/Vis absorption spectra show temperature-dependent absorption bands at around 305 and/or 345 nm, which according to DFT calculations correspond to the absorption of the carboxylate or phenolate proton transfer species, respectively. In solution, indications of the phenolate species are found only in a very apolar solvent (cyclohexane). Because of excited-state relaxation, emission always occurs from the phenolate structure, which explains the large Stokes shift.

Solubility Measurement and Modeling of 2-Amino-4,6-dichoropyrimidine in Ten Pure Solvents and (Ethyl Acetate + Ethanol) Solvent Mixtures

The basis of purification and further theoretical studies of 2-amino-4,6-dichoropyrimidine is the solubility and solution thermodynamics in different solvents. In this paper, the solubility of 2-amino-4,6-dichoropyrimidine in 10 neat solvents (methanol, ethanol, n-propanol, isopropanol, acetone, acetonitrile, ethyl acetate, 1,4-dioxane, toluene, and cyclohexane) and binary liquid mixtures (ethyl acetate + ethanol) was measured by the isothermal saturation method at temperatures range from 278.15 to 318.15 K, at p = 101.2 kPa. High-performance liquid chromatography (HPLC) was used to analyze the solubility of 2-amino-4,6-dichoropyrimidine in selected solvents. To sum up, the equilibrium mole fraction solubility was highest in 1,4-dioxane (2.619 × 10–2 at 318.15 K) and lowest in cyclohexane (0.02238 × 10–2 at 318.15 K), and ranked as 1,4-dioxane (2.619 × 10–2 at 318.15 K) > acetone (1.630 × 10–2 at 318.15 K) > ethyl acetate (1.471 × 10–2 at 318.15 K) > acetonitrile (0.5048 × 10–2 at 318.15 K) > methanol (0....

Exploring and elaborating the excited state mechanism of a novel AIE material 2-(5-(4-carboxyphenyl)-2-hydroxyphenyl)benzothiazole

A novel aggregation-induced emission material 2-(5-(4-carboxyphenyl)-2-hydroxyphenyl)benzothiazole (2-CHBT) has been investigated based on density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. Via reduced density gradient (RDG) versus sign(λ2)ρ analyses, we firstly verify the formation of intramolecular hydrogen bond in 2-CHBT system. Analyzing the primary geometrical parameters in 2-CHBT and comparing the changes about infrared (IR) vibrational spectra, we confirm that the hydrogen bond O-H···N is strengthened in the S1 state upon excitation. Exploring photo-excitation process, the frontier molecular orbitals (MOs) and charge density difference (CDD) analyses have been performed using TDDFT/B3LYP/TZVP theoretical level, based on which we verify the charge transfer phenomenon referring to the S0 → S1 transition. And the CDD around the hydrogen bond moiety provides the tendency of ESIPT for 2-CHBT molecule. Comparing the energy gap between HOMO and LUMO orbitals in cyclohexane, toluene, chloroform, and DMSO solvents, we predict the ESIPT reaction might be more active in non-polar solvents. In addition, constructing potential energy curves and searching transition state (TS) structures, we further clarify the ESIPT mechanism and verify that non-polar solvents might facilitate the ESIPT process. Our simulated results reappear experimental spectral results and successfully explain experimental phenomenon.

Solubility of 2-Chlorophenylacetic Acid in 12 Pure Solvents from T = (273.15/283.15 to 318.15) K: Determination and Modeling

The solubility data of 2-chlorophenylacetic acid in solid–liquid equilibrium were indispensable for a preliminary industrial application aimed at purifying and renewing. In this paper, the solubilities of 2-chlorophenylacetic acid in 12 alternative solvents (toluene, water, acetonitrile, ethylacetate, ethylbenzene, n-propanol, isopropanol, n-butanol, isobutanol, cyclohexane, 2-butanone, and acetone) at atmospheric pressure and temperatures ranging from 273.15/283.15 to 318.15 K were determined by the isothermal saturation method. Upon the analysis of the experimental data, the mole fraction solubility increased when the solution temperature increased. Generally, the solubility order in different solvents is as follows: 2-butanone > (acetone, isopropanol, ethylacetate, n-propanol, isobutanol, n-butanol) > acetonitrile > toluene > ethylbenzene > cyclohexane > water. Thermodynamic models such as the modified Apelblat equation, λh equation, Wilson model, and NRTL model were chosen to fit and correlate the obtained solubility data. Some association parameter could be obtained. The maximum value of root-mean-square deviation (RMSD) is 48.72 × 10–4, and the maximum relative mean deviation (RAD) is 1.86%. Besides, the mixing properties of the solutions were obtained, including the mixing Gibbs energy, mixing enthalpy, mixing entropy, activity coefficient at infinitesimal concentration (γ1∞), and reduced excess enthalpy (H1E,∞). The course of dissolution is spontaneous, though the study of solubility and thermodynamics was helpful to the purification process of 2-chlorophenylacetic acid.

Application of featured microwave-metal discharge for the fabrication of well-graphitized carbon-encapsulated Fe nanoparticles for enhancing microwave absorption efficiency

Carbon-encapsulated iron nanoparticles (Fe@CNPs) with a high degree of graphitization, good integrity in the graphite shells, and high microwave-absorbing capability were prepared by first dissolving ferrocene into organic solvent and then being carbonized by MW-metal discharges under inert atmosphere. Four different organic solvents (benzene, cyclohexane, paraffin, and anhydrous ethanol) were tested, and well-graphitized Fe@CNPs were formed when using benzene or cyclohexane as the solvent. The use of MW-metal discharges with low-toxic cyclohexane and ferrocene as raw materials provides a new method for the preparation of Fe@CNPs with the merits of simplicity, low environmental impact, and high efficiency. The fabricated Fe@CNPs have excellent microwave-absorbing capability, which is respectively 29, 19.3, and 9.7 times those of carbonyl iron powder, SiC, and carbon nanotubes after 1-min microwave irradiation at 1000 W. The thermal gravimetric analysis demonstrates that the fabricated Fe@CNPs have good thermal stability. Owing to these properties, Fe@CNPs have the potential to shape nanoscale or micron scale high-energy sites for a vast variety of applications in the field of microwave chemistry.

Solubility Measurement and Correlation for ε-2,4,6,8,10,12-Hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane in Different Alkanes/Aromatic Hydrocarbon + Ethyl Acetate Binary Solvents at Temperatures of between 283.15 and 323.15 K

The solubility data of ε-2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane in six binary solvents (n-hexane, n-heptane, n-octane, isooctane, cyclohexane, and methylbenzene mixed with various mole fractions of ethyl acetate) was experimentally studied by the gravimetric method at temperatures ranging from 283.15 to 323.15 K under an atmosphere pressure of 0.1 MPa. The results of these measurements were correlated with the modified Apelblat equation, CNIBS/R-K equation, and Jouyban–Acree model. All three models provide a satisfactory correlation.

Isolation and Characterization of Bacillus megaterium IBBPo17 a Solvent-Tolerant Bacterium

A new solvent-tolerant Gram-positive bacterium was isolated from an oily sludge sample. The isolated bacterium was identified based on phenotypic characteristics and 16S rRNA gene sequence as Bacillus megaterium IBBPo17 (GenBank KX499518). Two catabolic genes, such as alkane hydroxylase (alkB1) and naphthalene dioxygenase (ndoM) were detected in the genome of this solvent-tolerant Gram-positive bacterium. B. megaterium IBBPo17 could survive and grow in the presence of toxic organic solvents, such as n-alkanes (n-decane, n-hexane) and cyclic solvents (cyclohexane, ethylbenzene, styrene, toluene). Short-chain n-alkanes (n-hexane, n-decane) with a high logarithm of the partition coefficient of the solvent in octanol–water mixture (log POW) were less toxic for B. megaterium IBBPo17, while cyclic solvents (cyclohexane, toluene, styrene, ethylbenzene) with a lower log POW were more toxic for this bacterium. B. megaterium IBBPo17 produced both extracellular enzymes (i.e., protease, amylase, cellulase) and extracellular surfactants, which are well-known for their broad potential applications. Changes in the cell ultrastructure, protein and lipid profiles were depicted as an adaptive feature when B. megaterium IBBPo17 cells were exposed to these organic solvents.

A remarkable solvent effect on reductive amination of ketones

We report the first systematic study of solvent effect on reductive amination of ketones with ammonia and dihydrogen (H2) over Ru/C, Rh/C, Pd/C and Pt/C catalysts. Protic (water, methanol, ethanol and isopropanol), aprotic polar (dioxane and tetrahydrofuran) and aprotic apolar (cyclohexane and toluene) solvents were investigated. Reaction kinetic model was built to reveal solvent-dependent reaction pathway and solvent-related rate constant for individual steps. Primary amine is produced via two distinct routes, i.e., hydrogenation of imine and hydrogenolysis of Schiff base adduct. These two routes co-exist in organic solvents, while the preference of which route to take heavily depends on the nature of the solvent. In contrast, the formation of imine and Schiff base are not favored in water, resulting in high selectivity towards alcohol. Methanol is identified as the best solvent for reductive amination of ketones, attributed to the highest rates for imine and Schiff base formation compared to other solvents, as well as high hydrogenation activity.

Unveiling the mechanism of the promising two-dimensional photoswitch — Hemithioindigo

The control of internal molecular motions by outside stimuli is a decisive task in the construction of functional molecules and molecular machines. Light-induced intramolecular rotations of photoswitches have attracted increasing research interests because of the high stability and high reversibility of photoswitches. Recently, Henry et al. reported an unprecedented two-dimensional controlled photoswitch, the hemithioindigo (HTI) derivative Z1, whose single bond rotation in dimethyl sulphoxide (DMSO) solvent and double bond rotation in cyclohexane solvent can be induced by visible light (J. Am. Chem. Soc. 2016, 138, 12,219). Here we investigate the intramolecular rotations of the HTI and Z1 in different polar solvents by time-dependent density functional theory (TDDFT) and Nonadiabatic dynamic simulations. Due to the steric hindrance between methyl and thioindigo fragment, the rotations of Z1 in the excited state are obstructed. Interestingly, the HTI exhibits two distinct rotation paths in DMSO and cyclohexane solvents at about 50fs. The intermolecular hydrogen bonds between HTI and DMSO play an important role in the rotation of HTI in DMSO solvent. Therefore, the HTI is a more promising two-dimensional photoswitch compared with the Z1. Our finding is thus of fundamental importance to understand the mechanisms of this class of photoswitches and design complex molecular behavior.

Comments on “Solubility and thermodynamic analysis of 1,6-hexanediamine in mono-solvents and 1-butanol + cyclohexane mixed solvents at different temperatures”

Errors are found in the authors' mathematical representation pertaining to the Jouyban-Acree model for describing the experimental mole fraction solubility of 1,6-hexanediamine in binary 1-butanol+cyclohexane solvent mixtures. The mathematical representation is corrected so that published equation coefficients give the authors' back-calculated mole fraction solubilities that are reported in the published paper.

Determination and Correlation for the Solubilities of Succinic Acid in Cyclohexanol + Cyclohexanone + Cyclohexane Solvent Mixtures

The solubilities of succinic acid in binary cyclohexanone + cyclohexanol solvent mixtures at 304.25–354.65 K, in binary cyclohexane + cyclohexanol solvent mixtures at 300.15–346.15 K, in binary cyclohexane + cyclohexanone solvent mixtures at 297.65–351.25 K, and in ternary cyclohexanol + cyclohexanone + cyclohexane solvent mixtures at 306.95–343.15 K were determined by the synthetic method at atmospheric pressure. The experimental solubility data in binary solvent mixtures were correlated by the Apelblat equation and nonrandom two-liquid (NRTL) activity coefficient model, and the calculated solubility data by the models have a good agreement with the experimental data. Then, the solubilities of succinic acid in ternary cyclohexanol + cyclohexanone + cyclohexane solvent mixtures were predicted by the NRTL model and compared with the experimental solubility data. Finally, the solubilities of succinic acid in the three studied binary solvent mixtures were compared with the solubilities of glutaric acid and a...

Synthesis, properties of pentaalkylguanidinium-based magnetic room temperature ionic liquids (MRTILs) and the mutual solubility of (MRTILs + cyclohexane) and (MRTILs + n-octane) binary systems

The application of guanidinium-based ionic liquids (ILs) is a newly emerging area in the fields of extraction desulfurization. Herein, four novel pentaalkylguanidinium-based magnetic room temperature ionic liquids (MRTILs) [CnTMG][FeCl3Br] (n = 2, 4, 6, 8) were synthesized and characterized by FT-IR, Raman and HRMS (ESI) spectra. The physical properties including thermal stability, density, viscosity, conductivity and magnetic properties were determined and revealed that the MRTILs were liquids at room temperature and have good thermal stability (Td > 250 °C), high magnetic susceptibility (>3.8 × 105 emu·g−1) and low viscosities (<160 mPa·s, 25 °C). Moreover, the mutual solubility behaviors for binary systems of MRTILs with representative non-polar organic solvents (cyclohexane, n-octane) were measured at temperatures from 5 to 65 °C, showed a low miscibility between MRTILs and organic solvents and a typical lower critical solution temperature (LCST) phenomenon. The results are supposed to provide useful information for further application as “green” liquid desulfurization extractants or others potential dispersive liquid-liquid microextraction applications.

New Insights on Hydrogen-Bond-Induced Fluorescence Quenching Mechanism of C102-Phenol Complex via Proton Coupled Electron Transfer.

The H-bonded coumarin 102 (C102)-phenol complex has been a model system usually used to understand the influence of H-bonding on photophysical processes. Zhao and Han first showed that significant H-bond strengthening occurs in the excited state and proposed the possibility of fluorescence quenching in the complex via internal conversion from a locally excited (LE) state to a low-lying charge transfer (CT) state. Later, we experimentally confirmed fluorescence quenching of C102-phenol complex in a nonpolar solvent (cyclohexane). However, we also found that the existence of the low-lying CT state is ambiguous. Here, we proposed an alternative mechanism for the fluorescence quenching in the H-bonded complex. For this, we evaluate the excited state potential energy surface considering complete H atom-transfer from phenol to C102 along the H-bonding coordinate. Surprisingly, we observed two distinct minima separated by a low-energy barrier. One minimum corresponds to the complex with shortening of H-bond consistent with that of Zhao and Han. On the other hand, the second minimum, which has even lower energy than the first minimum, is likely to be arising from the proton-coupled electron transfer (PCET) process. The nature of the lowest excited state alters from LE to CT type at the second minimum, which may account for the fluorescence quenching phenomena in the system.

Effects of styrene unit on molecular conformation and spectral properties of CN[sbnd]PhCH[dbnd]NPhCH[dbnd]CHPh[sbnd]CN

Compound CN-PhCH=NPhCH=CHPh-CN with both stilbene and benzylidene aniline units was synthesized, and studied from the viewpoint of molecular conformation and spectroscopic property by a combined use of experimental and computational methods. The maximum UV absorption wavelength (λmax) of the compound in ethanol, acetonitrile, chloroform and cyclohexane solvents were measured, and the 13C NMR chemical shift value δC(CN) in chloroform-d was determined. The crystal structure of the compound was determined by X-ray diffraction. The frontier molecular orbital was calculated by density functional theory method. The results show that the UV absorption spectrum of the titled compound is similar to those of Schiff bases, while there is a larger red shift of λmax comparing to that of CN-PhCH=NPh-CN. Moreover, the molecular configuration of the titled compound relative to CN is anti-form, having a more obvious twisted structure. The spectral and structural behaviors are further supported by the results of frontier molecular orbital analyses, NBO, electrostatic potentials and TD-DFT calculations. The study provides deeper insights into the molecular conformation of Schiff bases.

Fine tuning the emission wavelengths of the 7-hydroxy-1-indanone based nano-structure dyes: Near-infrared (NIR) dual emission generation with large stokes shifts

Near-infrared (NIR) fluorescent dyes have recently gained special attention due to their applications to use as molecular probes for imaging of biological targets and sensitive determination. In this study, photophysical properties of the 7-hydroxy-1-indanone based fluorophors A1, A2, A3, B1, B2 and 3R-B2 (R=CF3, NH2, NO2 and OMe) in the gas and three solution phases were probed using TD-DFT method at PBE0/6-311++G(d,p) and M06-2X/6-311++G(d,p) levels of theory. In addition to structural and photophysical properties as well as ESIPT mechanism of all mentioned molecules, the FC and relaxed potential energy surfaces of B2 and 3R-B2 (R=CF3 and NH2) molecules were explored in gas phase and acetonitrile, cyclohexane and water solvents. It is predicted that the A1, A3 and 3R-B2 chromophores afford normal (615–670nm) and NIR fluorescence emissions (770–940nm; biological window) with the large Stokes shifts of >160 and >300nm, respectively. A good aggrement was found between theoretical and experimental results. In sum, these new types of dyes may render the new approaches for the development of the most efficient NIR fluorescent probes for enhanced image contrast and optimal apparent brightness in biological applications.

Theoretical Insights Into the Excited State Double Proton Transfer Mechanism of Deep Red Pigment Alkannin.

As the most important component of deep red pigments, alkannin is investigated theoretically in detail based on time-dependent density functional theory (TDDFT) method. Exploring the dual intramolecular hydrogen bonds (O1-H2···O3 and O4-H5···O6) of alkannin, we confirm the O1-H2···O3 may play a more important role in the first excited state than the O4-H5···O6 one. Infrared (IR) vibrational analyses and subsequent charge redistribution also support this viewpoint. Via constructing the S1-state potential energy surface (PES) and searching transition state (TS) structures, we illuminate the excited state double proton transfer (ESDPT) mechanism of alkannin is the stepwise process that can be first launched by the O1-H2···O3 hydrogen bond wire in gas state, acetonitrile (CH3CN) and cyclohexane (CYH) solvents. We present a novel mechanism that polar aprotic solvents can contribute to the first-step proton transfer (PT) process in the S1 state, and nonpolar solvents play important roles in lowering the potential energy barrier of the second-step PT reaction.