• Bulletin of the Korean Chemical Society
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• 제20권5호
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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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• 제34권9호
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• pp.2711-2719
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• 2013

Hydrogen bonding interaction between alcohols and water molecules is an important characteristic in the aqueous solutions of alcohols. In this paper, a series of molecular dynamics simulations have been performed to investigate the aqueous solutions of low molecular weight alcohols (methanol, ethylene glycol and glycerol) at the concentrations covering a broad range from 1 to 90 mol %. The work focuses on studying the effect of the alcohols molecules on the hydrogen bonding of water molecules in binary mixtures. By analyzing the hydrogen bonding ability of the hydroxyl (-OH) groups for the three alcohols, it is found that the hydroxyl group of methanol prefers to form more hydrogen bonds than that of ethylene glycol and glycerol due to the intra-and intermolecular effects. It is also shown that concentration has significant effect on the ability of alcohol molecule to hydrogen bond water molecules. Understanding the hydrogen bonding characteristics of the aqueous solutions is helpful to reveal the cryoprotective mechanisms of methanol, ethylene glycol and glycerol in aqueous solutions.

• Journal of Ginseng Research
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• 제42권4호
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• pp.463-469
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• 2018

Background: Roots of Withania somnifera (WS) are a celebrated medicinal ingredient in Ayurvedic and many other indigenous systems of medicine. The present study investigates the effect of the phytochemical composition of the extracts on their antioxidant and reducing activities. Methods: WS roots were extracted with water, acetone, aqueous methanol (1:1), and methanol:-chloroform:water (1:1:1) to obtain aqueous, acetone, hydro-methanolic, and methanol-chloroform-water extracts. Thereafter, phytochemical constitution and antioxidant and reducing activities of the extracts were compared using different qualitative and quantitative tests. Results: Maximum extraction recovery was obtained with 50% aqueous methanol whereas extraction with acetone yielded the poorest recovery. Methanol-chloroform-water extract had the highest content of phytochemical constituents, except tannins, and also exhibited the highest antioxidant and reducing activities. Conclusion: Phytochemical composition and antioxidant and reducing activities of the extracts were positively associated with the use of organic solvents during the extraction process. Alkaloids and flavonoids were the most important contributors in the antioxidant and reducing activities of the extracts.

• KSBB Journal
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• 제18권5호
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• pp.347-351
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• 2003

초임계 이산화탄소를 이용하여 감초의 glycyrrhizic acid를 추출하기 위하여 일정 유속 (3 mL/min)에서 추출온도와 압력 보조용매의 종류와 첨가량에 대한 효과를 조사하여 보았다. 순수한 초임계 이산화탄소만을 사용해서 감초로부터 glycyrrhizic acid를 거의 추출할 수 없었다. 99.9% methanol, ethanol과 isopropanol을 보조용매로 초임계 이산화탄소에 첨가하여 추출한 경우, 추출수율의 증대에 큰 영향을 미치지 않았으나, 70% (v/v) aqueous methanol, ethanol과 isopropanol을 이산화탄소에 10% (v/v)으로 첨가한 경우에는 급격한 수율의 증대를 볼 수 있었고, 70% (v/v) aqueous methanol을 첨가하였을 때가 96.62 wt%로 가장 높은 회수율을 나타내었다. 한편, 70% (v/v) aqueous ethanol을 보조용매로 사용한 경우의 가장 높은 회수율과 빠른 추출속도를 나타낸 추출압력과 추출온도는 각각 40 MPa과 8$0^{\circ}C$였고, 이 조건하에서 다양한 농도의 aqueous ethanol (50∼90% (v/v))을 보조용매로 사용하였을 때 60% (v/v) aqueous ethanol을 보조용매로 첨가한 경우가 104.11 wt%로 가장 높은 회수율과 빠른 추출속도를 나타내었다. 또한 이산화탄소에 대한 60% (v/v) aqueous ethanol의 첨가량은 15% (v/v)을 첨가하였을 때 60분 내에 최고 회수율 (104.57 wt%)에 도달하였다.

• Bulletin of the Korean Chemical Society
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• 제26권2호
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• pp.238-240
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• 2005

The enthalpies of transfer, ${\Delta}H_t{\Theta}$, of NaI from water to aqueous methanol, ethanol and isopropanol, iPrOH, systems are reported. These data have been analysed in terms of the new solvation theory. These data are considered in terms of the new developed solvation theory including variable ($\alpha$n + $\beta$N), the net effect of the solute on the solvent-solvent bonding, is positive if there is a net breaking or weakening of solvent-solvent bonds. The solvation parameters recovered from the analyses indicate that the net affect of NaI on solvent structure is a breaking of solvent-solvent bonds and that NaI is preferentially solvated by water in all aqueous alcohol systems considered. ($\alpha$n + $\beta$N) values increase with increasing in the size of the alcohol alkyl residue from methanol to iPrOH.

• Bulletin of the Korean Chemical Society
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• 제18권9호
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• pp.1017-1021
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• 1997

Solvolyses of p-methoxyphenyl chloroformate in water, D2O, CH3OD, 50% D2O-CH3OD, and in aqueous binary mixtures of acetone, ethanol and methanol are investigated at 25.0 ℃. Product selectivities are reported at 25 ℃ for a wide range of ethanol-water and methanol-water solvent compositions. The Grunwald-Winstein plots of first-order rate constants for p-methoxyphenyl chloroformate with YCl (based on 1-adamantyl chloride) show marked dispersions into three separate curves for the three aqueous mixtures with a small m value and a rate maximum for aqueous alcohol solvents. Third-order rate constants, kww, kaw, kwa and kaa were calculated from the observed kww and kaa values together with kaw and kwa calculated from the intercept and slope of the plot of 1/S vs. [alcohol]/[water]. The calculated rate constants, kcalc and mol % of ester agree satisfactorily with those of the observed rate constants, kobs and mol % of ester, supporting the stoichiometric solvation effect analysis. The kinetic solvent isotope effects determined in water and methanol are consistent with the proposed mechanism of the general base catalyzed carbonyl addition-elimination.

• Bulletin of the Korean Chemical Society
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• 제13권6호
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• pp.647-649
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• 1992

The critical micelle concentration (CMC) values of cetylpyridinium chloride (CPC) in some alcohol-aqueous solutions were determined by UV-Vis spectroscopy at 25$25^{\circ}C$. The CMC of CPC was increased with the addition of methanol and ethanol, while with the addition of propanol it was decreased because of the solubilization of propanol into the micelle of CPC. The ratio (${\beta}$) of the number of counterions to that of surfactant ions associated into micelles in alcohol (methanol, ethanol and propanol) aqueous solutions was measured by using the Shinoda $equation^{17}$. The ratio of counterion binding to the CPC micelles in methanol-and ethanol-water mixtures was larger than in pure water, while the ratio in propanol-water mixture might be much decreased.

• Advances in Traditional Medicine
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• 제6권4호
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• pp.306-311
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• 2006

This communication emphasized upon the sensitivity of the crude extracts of clerodendrum inerme against some of the human pathogenic bacteria. Five plant extracts (Petrol, Benzene, Methanol, Ethly acetate and Aqueous) under six different concentrations(500 ${\mu}g/ml$, 1 mg/ml, 2 mg/ml, 5 mg/ml, 10 mg/ml and 15 mg/ml) were tested by disk diffusion method. Methanol, Ethyl acetate and Aqueous extracts of the plant showed significant inhibition against fifteen of the eighteen bacteria tested. No earlier report on antibacterial activity of this taxon could be found in literature.

• 공업화학
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• 제10권1호
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• pp.19-23
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• 1999

아질산염을 이용한 키토산의 부분가수분해 반응에서 반응이 진행됨에 따라서 탈아세틸화도는 감소하였으며 가수분해된 각 fraction에서의 탈아세틸화도는 50% 이하로 확인되었다. GPC를 이용하여 이들 각 유도체의 수평균분자량을 확인한 결과, 물-메탄올에 의한 침전물은 6000에서 4000의 분자량을 가지고 있었으며, 메탄올-아세톤에 의해서는 2000 이하의 분자량을 가지는 것을 얻을 수 있었다. 이때 다분산도는 1.7 이하로 분자량 분포가 좁은 분해물을 얻을 수 있었다. 각 fraction 별로 분자량에 따른 항균효과를 E. coli HB 101과 Bacillus subtilis PP 2에 대해서 시험한 결과 분자량이 5100인 fraction B($H_2O:MeOH=1:5$)가 가장 우수하였고, 모든 시료에서 그람양성균인 Bacillus subtilis PP 2에 대한 항균능이 그람음성균인 E. coli HB 101에 비해 우수하였다.

• KSBB Journal
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• 제8권3호
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• pp.224-229
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• 1993

The feeding effects of Rosa rugosa roots powder extracted with two different extracting solvents on lipid metabolism in rats were evaluated. Rats were fed with purified diets containing methanol or 70% aqueous acetone extracts at a 1% level for 4 weeks. In addition, to examine the effects of age, rats with different ages (4weeks old vs. 3 months old) were fed with purified diets containing methanol extracts at a 1% level for 4weeks. Feeding of methanol extracts decreased the concentration of triacylglycerol in serum and liver, whereas the aqueous acetone extracts lowered the concentration of liver triacylglycerol with concomitant elevation of the concentration of serum triacylglycerol. The methanol extracts ameliorated the degree of increase in the serum triacylglycerol level in relation to age and decreased especially the concentration of free fatty acid in serum of adult rats. The results suggested possibility that the regulatory mechanism responsible for triacylglycerol-lowering effects of Rosa rugosa roots extracts in the liver could be modulated by differences in the components of extracts due to the variation in extracting solvents, and that the methanol extracts might be effective in lowering an age-dependent increase in the concentration of serum and liver triacylglycerol in rats.