• Journal of the Korean Chemical Society
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• v.35 no.5
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• pp.443-451
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• 1991

The solvation numbers of some ions in water and of KCl in mixed solvent systems were measured using the conductometric method. Stoke's radii of ions in solution were calibrated by the Nightingale method and the solvation numbers of ions in mixed solvents were deduced by simple assumptions. The deduced solvation numbers of each solvent reasonably go with its selective properties of solvation. From the isosolvation point of ions, the selective properties of ionic solvation were discussed.

• Journal of the Korean Chemical Society
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• v.28 no.4
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• pp.210-216
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• 1984

Solvatochromic comparison methods were applied to determine Taft's solvent parameters, ${\pi}^{\ast}$(solvent polarity-polarizability), ${\alpha}$(solvent hydrogen bond donor acidity) and ${\beta}$ (solvent hydrogen bond acceptor basicity) for MeOH-MeCN solvent mixtures. Swain's solvent parameters A(anion solvation scale) and B(cation solvation scale) were also determined by least square fitting of kinetic data in the same binary solvent mixtures. It was found that: (i)${\beta}$ depends on the basicity of the solvent and increases with the MeOH content owing to the increase in polymeric structure of methanol; (ii) ${\pi}^{\ast}$depends on the dipole moment of the solvent and increases with the MeCN content of the solvent; (iii) ${\alpha}$ increases rapidly with the MeOH content as the hydrogen bond donor acidity of the solvent mixtures increases. Taft's reaction constants a and s and Swain's reaction constants a and b were determined for the reactions reported from our laboratory previously using solvent parameters determined in this work. No meaningful inter-relationship was found between the two set of reaction parameters, but a good linear correlation was found between the ratios a/s and a/b. Solvent effect on the reaction mechanism, substituent effect and leaving group ability were examined in the light of these reaction constants ratios.

• Journal of the Korean Chemical Society
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• v.39 no.8
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• pp.589-597
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• 1995

In water-ethanol systems, the limiting equivalent conductances of electrolytes were obtained using conductometric method. Using TATB method, the limiting equivalent ionic conductances of Li+, Na+, K+, Cl-, and Br- ions were also obtained. The effective radii of corresponding ions were determined using Nightingale method. From the volume of the solvation shell, the four solvation numbers were suggested. The reasonable solvation numbers (hH2O+hO) were estimated by comparing the values obtained by from the various suggested methods. The isosolvation point of ion in water-ethanol estimated was found to be larger than that of in water-methanol. This result agree with ET (solvent polarity) values of solvents. From the reasonable solvation numbers of ions in water-ethanol, the selective solvents of corresponding ions in water-ethanol were obtained.

• Journal of Life Science
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• v.25 no.12
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• pp.1458-1469
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• 2015

Many organic solvent-tolerant bacteria have been isolated from all environments such as soil, waste-water, even deep sea after first isolation report of organic solvent-tolerant bacterium. Most organic solvent- tolerant isolates have been determined to be Gram-negative bacteria, because Gram-negative bacteria have inherent tolerance property toward hostile organic solvents more than Gram-positive bacteria. The mechanisms of organic solvent tolerance have been elucidated extensively using mainly organic solvent-tolerant Gram-negative bacteria. The solvent-tolerance mechanisms in Gram-positive bacteria can be found in comparatively recent research. Organic solvents exhibited different toxicity depending on the solvent, and the tolerance levels of organic solvent-tolerant bacteria toward organic solvents were also highly changeable among species and strains. Therefore, organic solvent-tolerant bacteria could coped with solvent toxicity and adapted to solvent stress through the multifactorial and multigenic adaptative strategies. They could be survived even in the hyper concentrations of organic solvents by mechanisms which include: changes in cell morphology and cell behaviour, cell surface modifications, cell membrane adaptations, solvent excretion pumps, chaperones and anti-oxidative response. The aim of this work is to review the representative solvent tolerant bacteria and the adaptative and tolerance strategies toward organic solvents in organic solvent-tolerant bacteria, and their potential industrial and environmental impact.

• Applied Chemistry for Engineering
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• v.20 no.6
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• pp.685-691
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• 2009

Dispersions of fumed silica are made in 6 kinds of mono-solvents and mixed solvents which have hydroxyl group, non hydroxyl group, different polarity, and different molecular size. The viscosity and rheology behaviors of the each dispersion are investigated according to the viewpoint of solvent characteristic. The silica dispersion in polar solvent with hydroxyl group is stable and low viscous sol. The silica dispersion in non-polar solvent with non-hydroxyl group is high viscous gel. When the solvent with hydroxyl group is added to the silica dispersions with non-polar solvents, they show the reduction of viscosity with solvent content. They have minimum critical content which shows no viscosity change. The minimum critical solvent content is decreased according to the polarity of solvents with no hydroxyl group. The solvation layer which is formed on the silica surface through hydrogen bonding between hydroxyl-containing solvent and the silanol group of silica surface is the reason of stable and low viscous sol. In case of non-polar solvent, silanol on adjacent silica particles interacted directly by hydrogen bonding show high viscous and flocculated gel.

• Korean Chemical Engineering Research
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• v.58 no.1
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• pp.92-97
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• 2020

In this study, the solubilities of a pharmaceutical compound, nifedipine, in three mixed solvents were determined. In addition, the nifedipine, that was dissolved in solvents (acetone, DMF, methylene chloride), was recrystallized using antisolvents (water, hexane, carbon dioxide) The external shape, size, and melting point of the crystallized nifedipine were measured. As the mixed solvents, acetone+water, DMF+water, and methylene chloride+hexane were used, and the solubility of nifedipine decreased with increasing antisolvent concentrations in the mixtures. In case of acetone+water, the solubility maximum was observed due to the density anomaly of the mixture, and this phenomenon was not observed in other systems. The crystallized nifedipine particles exhibited the bladed, equant, and prismatic habits, and the particles size was significantly reduced compared to the raw material. The average particle size of raw nifedipine was 337 ㎛, and the size of crystallized particles was in the range of 11.6~69.8 ㎛. All the crystallized nifedipine particles had the same thermal behavior and this result was not influenced by the change of solvent and antisolvent.

• Journal of the Korean Chemical Society
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• v.36 no.6
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• pp.796-801
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• 1992

An empirical Lewis basicity, DN, for eight mixed methanol solvents has been measured by the solvatochromic behavior of the [Cu(tmen)(acac)]$CIO_4$. The change of DN in mixed methanol solvents is not correlated with composition of the mixtures and divided into three groups: (1) dipolar aprotic solvents contribute mainly to the solvation of solute (MeOH-DMSO, MeOH-PY, MeOH-DMF), (2) two components of mixture contribute equally to the solvation of solute (MeOH-MeCN, MeOH-dioxane, MeOH-AC) and (3) methanol contributes entirely to the solvation of solute (MeOH-DCE, MeOH-TCE). The relationship between DN and Kamlet-Taft's $B_{KT}$ for mixed methanol solvents was found to agree well. These DN values also were a useful factor to analysis of reactivity for mixed methanol solvents.

• Journal of the Korean Chemical Society
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• v.27 no.1
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• pp.1-8
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• 1983

Solvent effects on nucleophilic substitution reaction of naphthalene sulfonyl chlorides with pyridine in protic and aprotic solvent have been studied by means of conductometry. Results showed that the rate constants increased with dielectric constants for protic solvents, while they decreased with dielectric constants for aprotic solvents, except for acetonitrile which has a higher dielectric constant but had also greater rate constant. The rate constants were shown to be more susceptible to polarity-polarizability parameter, , than to hydrogen bond donor acidity parameter, ${\alpha}$, indicating that the pulling effect of hydrogen bonding solvent.

• KSBB Journal
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• v.16 no.1
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• pp.95-98
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• 2001

Various factors affecting the supercritical carbon dioxide extraction of daidzein from soybean were studied. Daidzein was not extracted with pure supercritical carbon dioxide. The ethanol was an efficient modifier for supercritical carbon dioxide to extract daidzein. The extraction efficiency increased as the pressure increased up to 300 bar. At $35^{\circ}C$ and 300 bar, 93% of daidzein was extracted with supercritical carbon dioxide modified with 15% of ethanol.

• Journal of the Korean Society of Industry Convergence
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• v.6 no.1
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• pp.31-36
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• 2003

8개의 수정진동자 위에 서로 다른 종류의 Lipid를 코팅하여서 만든 센서 배열을 가지고 유기용매를 인식할 수 있는 System을 구성한다. 유기용매 인식센서에 대한 수학적 모델을 사용하여 여러 가지 유기용매에 대한 센서의 응답으로부터 센서 표면과 유기용매 간의 물질 전달속도 패턴과 친화력 패턴을 얻어 유기용매 종류를 인식하였다. 패턴인식은 인공신경망을 이용하였으며 인공신경망의 연결 강도 수정은 Levenberg-Marquardt 알고리즘을 사용하였다. 신경망의 출력은 4개로 하였고, 디지털 신호인 0과 1의 조합으로 유기용매 종류를 구분하였다. 이 시스템을 이용하여 9개의 유기용매 Acetone, Benzene, Chloroform, Carbon-tetrachloride, Ethylacetate, Buthylacetate, Cyclohexane, Dichloromethane, 1,1,2,2,Tetrachloroethane, 2,2,4Trimethylpentane을 구분하여 인식할 수 있었다.