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The solubility and thermodynamic properties of thiamethoxam in six monosolvents [acetone, dichloromethane, dimethylformamide (DMF), methyl acetate, ethyl acetate, and 1-methyl-2-pyrrolidinone (NMP)...

2-Methylnaphthoquinone is an important chemical product. The catalyst used in the catalytic oxidation of 2-methylnaphthalene to 2-methylnaphthoquinone has been a research hotspot. In this paper, benzoxazine derived ordered mesoporous carbon materials were used as catalysts, and their catalytic performance in acetic acid/hydrogen peroxides was investigated. The N/S co-doped carbon material (NSCM) was prepared with thiourea-type benzoxazine as a carbon precursor and SBA-15 as a template. The nitrogen-doped carbon material (NCM) was prepared using the same method using aniline-type benzoxazine as a precursor. The carbon materials were characterized by N2 adsorption/desorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The results have shown that both carbon materials exhibit worm-like structure and have graphitized amorphous structure. Nitrogen in the carbon materials existed in the form of pyridine nitrogen and pyrrole nitrogen, which caused the surface defects of carbon materials. The surface defects are critical for the enhancement of the catalytic activity of carbon materials. With NSCM and NCM as catalysts, the yields of 2-methylnaphthoquinone were 78.8% and 65.7%, respectively. By comparison, NSCM has higher catalytic activity, and the catalytic activity remains stable after five cycles of use. These results indicate that NSCM has great potential as a highly efficient catalyst for the selective oxidation of 2-methylnaphthalene.

Solubility values of guanidine hydrochloride (GuHCl) in 11 different neat solvents namely “2-methoxyethanol, ethanol, N,N-dimethylformamide (DMF), n-propanol, 2-propoxyethanol, methanol, 2-ethoxyethanol, isopropanol, N-methyl pyrrolidone (NMP), 2-butoxyethanol and N,N-dimethylacetamide (DMAC)” were determined experimentally using a laser monitoring method under “p = 0.1 MPa”. The investigated temperature was set from 278.15 K to 323.15 K. The experimental results indicated that solubility of GuHCl increased with the increasing temperature. At 298.15 K, solubility of GuHCl was ranked as: DMF (0.4017) > DMAC (0.3400) > 2-methoxyethanol (0.3330) > 2-ethoxyethanol (0.2963) > 2-propoxyethanol (0.2158) > methanol (0.2017) > NMP (0.1704) > 2-butoxyethanol (0.1531) > ethanol (0.1174) > isopropanol (0.08857) > n-propanol (0.06604). Moreover, the effect of interactions between GuHCl and solvent molecules on solubility sequence was analyzed by solvation free energy or radial distribution function. The results acquired from molecular simulation analysis indicated that the whole dissolution behavior of GuHCl in investigated solvents was a complicated process. Furthermore, the recorded solubility of GuHCl was correlated and computed with the Two-Suffix Margules, nonrandom two-liquids (NRTL), Wilson and Apelblat model, which the Apelblat equation performed the best correlate results than another three models. Finally, thermodynamic mixing and dissolution properties were calculated on the basis of Wilson model, and the mixing and dissolution process were both found to be entropy-driven and spontaneous.

This work determined the mole fraction solubility of thiamethoxam in three binary solvent mixtures ((DMSO, DMA and acetic acid) + methanol) under the conditions of “T = 278.15 K to 323.15 K” and “p = 0.1 MPa”. The results demonstrated that with the increase of temperature and co-solvent mass fraction, the measured solubility of thiamethoxam increases in all the solvent mixtures studied. The results of using Hansen solubility parameters to investigate the affinity between thiamethoxam and the three mixed solvents studied indicate that this affinity may be caused by a combination of factors. Five thermodynamic models including modified Apelblat model, λh model, Wilson model, NRTL model and UNIQUAC model were used to regress the experimental solubility data of thiamethoxam in the three binary solvent mixtures. It was found that the UNIQUAC model and the modified Apelblat model correlated the experimental solubility more accurately than the other three models. In addition, the mixed thermodynamic properties for mixing process of thiamethoxam in different mixed solvents were estimated and discussed in term of Wilson model and experimental solubility data of thiamethoxam. Moreover, Wilson model was used to calculate the mixing thermodynamic parameters (ΔmixG, ΔmixH, ΔmixS) of the mixing process of thiamethoxam. All ΔmixG and ΔmixH values are negative and ΔmixS values are positive, which indicate that the mixture process of thiamethoxam in all the binary solvent mixtures studied is an entropy driven and spontaneous endothermic process.

Ipriflavone is a drug widely used in clinical treatment and prevention of osteoporosis, and it also has a certain protective effect on the nervous system. In this work, the laser dynamic method was used to measure the solubility data of IP in three binary solvents under normal pressure (temperature range: 278.15 K to 323.15 K). The results show that as both the mass fraction of positive solvents (NMP, DMF, DMAC) in the binary mixed solvents and the temperature increase, the solubility of IP increases. In addition, the Hansen solubility parameter (HSP) was used to analyze the order of solubility. The results indicated that the selected solubility parameters (Δδd, Δδp, Δδh, Δδt and Δδ) could explain the solubility trend well. Furthermore, the modified Apelblat equation, λH equation, NRTL model and UNIQUAC model were used to correlate the solubility data in binary mixed solvents. By calculating the deviation between the experimental data and the fitting data, it shows that the selected models have a good correlation with the solubility data of IP. Finally, the modified van’t Hoff equation was used to calculate the apparent thermodynamic properties of IP during the dissolution process. The results show that the dissolution process is always endothermic and entropy driven.