• Bulletin of the Korean Chemical Society
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• v.20 no.5
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• pp.573-576
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• 1999

The rate constants and kinetic solvent isotope effects (KSIE, KMeOH/kMeOD) for solvolyses of para-substituted phenylchloroformates in CH3OH, CH3OD, H2O, D2O, 50% D2O-CH3OD were determined at 15.0 and 25.0℃ using conductometric method. Kinetic solvent isotope effects for the solvolyses of para-substituted phenyl chloroformates were 2.39-2.51, 2.21-2.28, and 1.67-1.69 for methanol, 50% aqueous methanol, and water, respectively. The slopes of Hammett plot for solvolysis of para-substituted phenyl chloroformates in methanol, 50% aqueous methanol, and water were 1.49, 1.17 and 0.89, respectively. The Hammett type plot of KSIE, log (KSIE) versus p, can be a useful mechanistic tool for solvolytic reactions. The slopes of such straight lines for para-substituted phenyl chloroformates are almost zero in methanol, 50% aqueous methanol, and water. It was shown that the reaction proceeds via an associative SN2 and/or general base catalysis addition-elimination (SAN) mechanism based on activation parameters, Hammett p values, and slopes of Hammett type plot of KS-IE.

• Bulletin of the Korean Chemical Society
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• v.6 no.5
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• pp.259-263
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• 1985

Rate Constants for the solvolysis of p-methylbenzyl chloride in various ethanol-water mixtures were studied at 30 and $40^{\circ}C$ under various pressures up to 1600 bar. The rates of reaction were increased with increasing temperature and pressure, and decreased with increasing solvent composition of ethanol mole fraction. From the rate constants, the values of the activation parameters (${\Delta}V^{\neq},{\Delta}{\beta}^{\neq},{\Delta}H^{\neq}\;and\;{\Delta}S^{\neq}$) were evaluated. The values of ${\Delta}V^{\neq}\;and\;{\Delta}{\beta}^{\neq}$ exhibit the extremum behavior at about 0.30 mole fraction of ethanol. This behavior is discussed in terms of solvent structure variation (electrostriction). From the relation between the reaction rate and the dielectric constant of solvent or the number of water molecule participated in the transition state, it could be postulated that the reaction proceeds through $S_N1$ mechanism.

• Journal of Life Science
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• v.23 no.10
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• pp.1246-1251
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• 2013

An organic solvent-tolerant lipase of Pseudomonas sp. BCNU 154 that was isolated from wastewater in the industrial complex region had optimal activity at $37^{\circ}C$ and pH 8. This crude extracellular lipase from BCNU 154 exhibited maximum stability in toluene, retaining about 6.01 U/ml (117.53%) activity for 2 h. $Ca^{2+}$, $Mg^{2+}$, $NH_4{^+}$, and $Na^+$ ions and triton X-100 activated the enzymes, whereas $Ba^{2+}$, $Hg^{2+}$, and $Zn^{2+}$ ions inhibited their activity. Pseudomonas sp. BCNU 154 lipase revealed stable activity comparable to that of the commercial immobilized Novozym 435. Thus, this organic solvent-tolerant lipase could have potential as a whole cell biocatalyst in industrial chemical processes without the use of immobilization.

• Journal of the Korean Applied Science and Technology
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• v.33 no.3
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• pp.459-465
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• 2016

This study investigated reusability of costly guard column by ultrasonic. It also investigated various effects that affect to guard column generation by ultrasonic. When investigated 30 KHz of frequency, area of ascorbic acid is 73.0% compared to unused guard column. As a result of investigation of effect of pH, guard column by ultrasonic is effective at alkali area. As a result of investigation of solvent effect, when ethanol is used, generation rate is 81.9% as of peak area compared to the case of analysis in un used column. From the result, it indicates that regenerated guard by ultrasonic is reusable.

• The Korea Journal of Herbology
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• v.22 no.4
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• pp.29-34
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• 2007

Objective : Kyenegum(Galli Stomachichum Corium) has been popularly used long as the digestive. The purpose of this study was to investigate the enzymatic characteristic of Kyenegum crude enzyme. Methods : To evaluate of the enzymatic characteristic of Kyenegum, we examined the activity of Kyenegum crude enzyme from optimum solvent, optimum temperature and pH of crude Kyenegum extract. Futhermore, we examined the effects of NaCI and acidity of crude Kyenegum extract. Results : The Kyenegum was composed with crude protein about 20%, crude lipid 2%. The optimum Kyenegum dry condition, optimum extract solvent, optimum temperature and optimum pH were $4{\sim}6$ hours at $60^{\circ}C$, commercial apple vinegar, $50^{\circ}C$ and 2.0. Conclusion : The result suggests that the Kyenegum crude enzyme extract very strong enzyme in temperature, NaCl and acidity, respectively.

• Textile Coloration and Finishing
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• v.13 no.5
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• pp.10-10
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• 2001

The Purpose of this study was to investigate spectrophotometric characteristics of Korean knotweed extracts. The properties were evaluated by it′s extracting solvent, effect of metallic ion, variations of pH values and effect of light exposure. The results were as following; The highest absorbance was found in methanol extract of Korean knotweed, while the lowest absorbance was carbon tetrachloride extract. The UV-vis. spectra of Korean knotweed colors in several solvents showed hypsochromic shift of n-π/sup ＊/ transition with the polarity of solvent. Absorbance and peak of UV-vis. spectra of Korean knotweed colors became lower and broader by addition of metallic ion. The light stability in irradiation with xenon ]amp of the color solution with Cu were higher than those of Al and Fe. The UV-vis. spectra of Korean knotweed extracts in various pH values showed bathochromic shift under alkaline condition, and their peaks disappeared after 5 hours exposure.

• Textile Coloration and Finishing
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• v.13 no.5
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• pp.298-305
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• 2001

The Purpose of this study was to investigate spectrophotometric characteristics of Korean knotweed extracts. The properties were evaluated by it's extracting solvent, effect of metallic ion, variations of pH values and effect of light exposure. The results were as following; The highest absorbance was found in methanol extract of Korean knotweed, while the lowest absorbance was carbon tetrachloride extract. The UV-vis. spectra of Korean knotweed colors in several solvents showed hypsochromic shift of $n->\pi^*$ transition with the polarity of solvent. Absorbance and peak of UV-vis. spectra of Korean knotweed colors became lower and broader by addition of metallic ion. The light stability in irradiation with xenon ]amp of the color solution with Cu were higher than those of Al and Fe. The UV-vis. spectra of Korean knotweed extracts in various pH values showed bathochromic shift under alkaline condition, and their Peaks disappeared after 5 hours exposure.

• Journal of Integrative Natural Science
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• v.10 no.4
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• pp.225-231
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• 2017

Cryptand resins were synthesized by mixing 1-aza-18-crown-6 macrocyclic ligand with styrene divinylbenzene copolymer having 1%, 2%, 5%, and 10% crosslink by a substitution reaction. These synthetic resins were confirmed by chlorine content, elementary analysis, SEM, surface area, and IR-spectrum. As the results of the effects of pH, crosslink of synthetic resin, and dielectric constant of a solvent on uranium ion adsorption for resin adsorbent, the uranium ion showed high adsorption at pH 3 or over. Adsorption selectivity for the resin in methanol solvent was the order of uranium ($UO_2{^{2+}}$) > calcium ($Ca^{2+}$) > neodymium ($Nd^{3+}$) ion, adsorbability of the uranium ion was the crosslink in order of 1%, 2%, 5%, and 10% and it was increased with the lower dielectric constant.

• Journal of Industrial Technology
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• v.19
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• pp.189-195
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• 1999

A study on the separation Cu, Ni, and Co was carried out using LIX 84 leachate, chelate extractant. For this test, artificial test solution was prepared by varing concentrations of Cu, Ni, Co, $(NH_4)_2CO_3$ and $(NH_4)_2SO_4$. It found that pH of the solution was very important factor for the separation of nickel from copper. The results showed that nickel was effectively extracted from copper by using LIX 84 at pH 1.0 to 1.2. The volume ration or organic to aqueous phases was 1.0. According to the McCabe-Thiele diagram, the extraction rate of copper was 99 percents at the equal ratio of organic to aqueous phase in three stages.

• Archives of Pharmacal Research
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• v.28 no.5
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• pp.612-618
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• 2005

A mucoadhesive microsphere was prepared by an interpolymer complexation and solvent evaporation method, using chitosan and poly(acrylic acid) (PAA), to prolong the gastric resid ence time of the delivery system. The Fourier transform infrared results showed that microspheres were formed by an electrostatic interaction between the carboxyl groups of the PAA and the amine groups of the chitosan. X-ray diffraction and differential scanning calorimetry analysis showed that the enrofloxacin in the chitosan-PAA microsphere was molecularly dispersed in an amorphous state. Scanning electron microscopy of the surface and the quantity of mucin attached to the microspheres indicated that chitosan-PAA microspheres had a higher affinity for mucin than those of chitosan alone. The swelling and dissolution of the chitosan-PAA microspheres were found to be dependent on the pH of the medium. The rate of enrofloxacin released from the chitosan-PAA microspheres was slower at higher pH; therefore, based on their mucoadhesive properties and morphology, the chitosan-PAA microspheres can be used as a mucoadhesive oral drug delivery system.