• Bulletin of the Korean Chemical Society
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• v.20 no.5
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• pp.577-580
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• 1999

Solvolyses of phenyl chlorothionoformate in water, D2O, CH3OD, 50% D2O-CH3OD, and in aqueous binary mixtures of acetone, ethanol and methanol are investigated at 25.0℃. The Grunwald-Winstein plots of firstorder rate constants for phenyl chlorothionoformate with Ycl (based on 2-adamantyl chloride) show a dispersion phenomenon, and also the extended Grunwald-Winstein plots show a poor correlation for the solvolyses of phenyl chlorothionoformate. The ring parameter (I) has been shown to give considerable improvement when it is added as an hI term to the original and extended Grunwald-Winstein correlations. The dispersions in the Grunwald-Winstein correlations in the present studies are caused by the conjugation between the reaction center and the aromatic ring in the vicinity of the reaction center. This study has shown that the magnitude of l and m values associated with a change of solvent composition leads to predict the SN2 transition state. The kinetic solvent isotope effects determined in deuterated water and methanol are consistent with the proposed mechanism of the general base catalyzed SN2 mechanism.

• Bulletin of the Korean Chemical Society
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• v.23 no.1
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• pp.123-131
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• 2002

Solvolyses rate constant of 1- and 2- naphthoyl chlorides (1 and 2) are reported for aqueous binary mixtures with methanol, ethanol, fluorinated alcohol, acetonitrile and dioxane. Kinetic solvent isotope effects (KISE) in methanol and product selectivities (S) of 2-naphthoyl chloride (2) in alcohol-water are also reported. Dispersions in Grunwald-Winstein correlations $(r{\leq}0.901)$ are discussed by multiple regression analysis incorporating ionizing power $(Y_{Cl})$ scale and rate-rate profiles. Major causes for these phenomena are investigated as an aromatic ring solvation effects, in conjunction with weakly nucleophilic solvation effects ($S_N2$ character), for solvolyses of 1 and for solvolyses of 2, as dual reaction channels, described as $S_N1$-$S_N2$ and $S_AN$-$S_N2$ processes. Distinct border lines between the two pathways are derived from solvolyses rates of 2 in 18 solvent using the results of $log(k/k_o)=mY_{Cl}+lN_T+hI$ plot with values of 1.13 for m, 0.37 for l and 0.15 for h value in 5 aqueous fluorinated alcohol mixtures. Using rate-product correlation, the validity of a third order model based on a general base catalyzed by solvent and contribution from these rate constants, $k_{aa},\;k_{aw}$ and $k_{aw}$, are investigated for $S_AN$-$S_N2$ solvolyses of 2 favored in more rich alcohol media and gradual addition of water to alcohol solvent shows a great shift away from stoichiometric solvation to predominantly medium effects. Rate-rate correlation between solvolyses of 2 and trimethyl acetylchloride (5) with alkyl group in the 29 aqueous solvent mixtures shows appreciable linearity (slope = 0.84, r = 0.987), caused by the same pathway ($S_N1$-$S_N2$ process), even if this correlation coincides with appreciable dispersion (different solvation effect).

• Textile Coloration and Finishing
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• v.11 no.5
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• pp.44-54
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• 1999

Poly(ethylene 2,6-naphthalate), PEN, is a relatively well-known polymer used for engineering purposes. Naphthalene ring provides rigidity to the polymer backbone, thus, it elevated the glass transition temperature and enhanced mechanical properties. The structure and properties of PEN affect a processing conditions severely, and the high-thermal stability have been had a poor thermal processibility. Hence, the basic mechanism of solvent drawing, is very much the same as that of thermal drawing from glassy state since both involve the inducement of segmental mobility. The former achieves the goal by use of chemical energy, and the latter does so by use of thermal energy. Generally, the sorption of the solvent by the polymer has a plasticizing effect, and leads to a lowering of the glass transition temperature, $T_g$. In this paper, the dynamic viscoelasticity behavior in liquid-drawing process of an unoriented amorphous PEN films were investigated using Rheovibron. The results are as follows ： (1) For the drawing in silicone oil, the drawing below $T_g$. had $\alpha{2}$-dispersion due to an inhomogeneous taut structure. (2) For the drawing in water, the inhomogeneous taut structure reduced by the effect of plasticization even below $T_g$. (3) For the drawing in butanol, the only aliphatic segment in PEN have some molecular mobility but the mobility of the aromatic segment having naphthalene ring is nearly impossible. (4) For the drawing in dioxane/water mixing solvent, the solvent effect is complementary each other and accordingly the entire molecular conformation have stable state. (5) For the drawing in dioxane/butanol mixing solvent, the inhomogeneity of the taut structure and the aromatic segment increase with increasing the temperature and this tendencies correspond with that of the draw ratio.

• Journal of the Korean Society of Food Science and Nutrition
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• v.29 no.5
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• pp.900-907
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• 2000

The antioxidant effects of dichloromethane, ethylacetate or water fraction of kimchi added to the 1% cholesterol diet were studied. Six New Zealand white rabbits in each group were fed either control diet (basal diet containing 1% cholesterol) or experimental diet containing dichloromethane (CH$_2$Cl$_2$), ethylacetate (EtOAc) or water ($H_2O$) fraction of kimchi in the control diet for 16 weeks. The amount of each solvent fraction of kimchi added to the experimental diet was equivalent to 5% of freeze-dried kimchi. Levels of hepatic lipid oxidation expressed as TBARS or peroxide value for the experimental groups were lower than that of control (p<0.05). Liver homogenated of the experimental group containing dichloromethane fraction of kimchi inhibited LDL oxidation in the presence of Cu++ by 46% (p<0.05). The activities of catalase, Glutathione peroxidase (GSH-Px), Cu, Zn-superoxide (Cu, Zn-SOD) and Mn-superoxide (Mn-SOD) of experimental groups were lower than those of control group. Low enzyme activities observed from the kimchi solvent fraction groups might be due to the level of lipid oxidation progressed less in these groups. The most significant antioxidant effects were observed from dichloromethane fraction of kimchi among the experimental groups. The major fatty acids of hepatic phospholipid of rabbit were C18:2 and C18:0. But the major fatty acid profile was changed into C16:0, C18:0, C18:1, and C18:2 when rabbit was fed 1% cholesterol diet for 16 weeks, and this profile was almost the same as in rabbit fed diet containing kimchi solvent fraction. The ratio for unsaturated fatty acid to saturated fatty acid decreased by cholesterol induced diet and it was not corrected by kimchi solvent fractions.

• The Korea Journal of Herbology
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• v.38 no.3
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• pp.19-26
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• 2023

Objectives : Agrimoniae Herba is a herbal medicine widely distributed in Asia and contains flavonoids including catechin, quercitrin, rutin, hyperoside, and quercetin. This study aimed to investigate the anti-oxidant activity and skin barrier function of different solvent fractions (Hexane; methylene chloride, MC; ethyl acetate, EA; n-butanol, Bu; Water) obtained from Agrimoniae Herba. Methods : Anti-oxidant activity of different solvent fractions obtained from Agrimoniae Herba was investigated through total polyphenol contents, total flavonoid contents, 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity, and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activity measurements. Then, filament aggregating protein (Filaggrin), Type I collagen, ceramide synthase (CERS) 3, and CERS4 were analyzed to evaluate the skin barrier strengthening effect of different solvent fractions obtained from Agrimoniae Herba on UVB-stimulated HaCaT cells. Results : As a result of measuring total polyphenol contents, total flavonoid contents, DPPH free radical scavenging activity, and ABTS radical scavenging activity, antioxidant activity was found to be excellent in the order of EA > Bu > MC > Hexane > Water. As a result of measuring mRNA gene expression of Type I collagen, Filaggrin, CERS3, and CERS4 after UVB-stimulated was applied to HaCaT cells treated with different solvent fractions obtained from Agrimoniae Herba, it was found to increase significantly in the Bu-treated group. Conclusion : Our findings show that the Bu sample obtained from Agrimoniae Herba has excellent anti-oxidant ability, which increases Type I collagen, Filaggrin, and ceramide synthetase in UVB-stimulated HaCaT cells to control the skin barrier improvement effect.

• The Korean Journal of Food And Nutrition
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• v.30 no.1
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• pp.51-58
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• 2017

Antioxidant activities of 80% methanol, water, and 70% ethanol extracts of Lentinula edodes GNA01 were compared and estimated. The yield of Lentinula edodes GNA01 was identified to be in the following order: water>70% ethanol>80% methanol, but there was no significant difference between 80% methanol and 70% ethanol extracts. The highest total phenolic content (TPC) and total flavonoid content (TFC) were found in water extract, and TPC of 80% methanol extract was higher than that of 70% ethanol extract and TFC of 70% ethanol extract was higher than that of 80% methanol extract. Water extract exhibited the strongest DPPH, ABTS radicals, and nitrite scavenging activities, $Fe^{2+}$ chelating ability, and FRAP among the three extracts. In addition, antioxidant activity of 80% methanol extract was higher than that of 70% ethanol extract in most of the experiments. As a result, antioxidant activity of Lentinula edodes GNA01 showed a difference according to extraction solvent and concentration; nevertheless, water extract exhibiting high polarity had the strongest antioxidant effect. Consequently, water extract from Lentinula edodes GNA01 is anticipated to be useful for the development of a high value-added functional product.

• Journal of the Korean Chemical Society
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• v.17 no.6
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• pp.411-415
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• 1973

The reaction between cyanide ion and triphenyl methane dyes is subject to marked catalysis by cationic micelles of cetyltrimethyl ammonium bromide(CTABr) and retarded by anionic micelles of sodium lauryl sulfate(NaLS). Added salts, anions inhibit the catalysis by CTABr, and cations, especially $Zn^{++},\;Cd^{++}$ decrease the retardation of the reaction rates in the presence of NaLS. The kinetic effects of the ionic micelles are much larger in water than in ethanol-water, methanol-water, propanol-water and acetone-water, but strange solvent effects, acceleration the reaction rates, was found in the reaction with malachite green in water-methanol system.

• Bulletin of the Korean Chemical Society
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• v.17 no.6
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• pp.520-524
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• 1996

Solvolyses of phenyl 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 phenyl chloroformate with YCl (based on 2-adamantyl chloride) show marked dispersions into three separate lines for the three aqueous mixtures with a small m value (m< 0.2) 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 and/or carbonyl addition for phenyl chloroformate solvolyses based on mass law and stoichiometric solvation effect studies.

• Korean Journal of Oriental Medicine
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• v.18 no.3
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• pp.147-154
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• 2012

Objectives : This study was performed to find best extraction solvent for application of Ulmi cortex to food or herbal medicine as an antioxidant only using water, ethanol and their mixtures. Methods : The Ulmi cortex extracts were prepared using water and 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% and 100% (v/v) ethanol, and were evaluated yields, total polyphenol contents, DPPH and ABTS radical scavenging activities, lipid peroxidation activities, and catechin and epicatechin contents. Results : Among the Ulmi cortex extracts, the yield was highest in water extract (8.9%) and lowest in ethanol extract (3.8%). The yield of 30% ethanol extract (8.5%) also was very high to similar with water extract. The total polyphenol content was highest in the 30% ethanol extract ($253.6{\mu}g/mg$ extract) and lowest in water extract ($109.0{\mu}g/mg$ extract). The DPPH radical scavenging activity was highest in ethanol extract (IC50, $8.53{\mu}g/ml$), ABTS radical scavenging activity was highest in 60% ethanol extract (IC50, $3.08{\mu}g/ml$), and the inhibition of lipid peroxidation was highest in 70% ethanol extract (IC50, $7.96{\mu}g/ml$). As ethanol content of extraction solvent increased from 0% to 30%, the antioxidant activities were remarkably increased whereas from 30% to 100%, the antioxidant activities were increased or decreased a little. Conclusions : The findings of the present study suggest that 30% ethanol is best solvent for extraction of Ulmi cortex, considering yield, polyphenol content, and antioxidant activities with extraction cost.

• Journal of the Mineralogical Society of Korea
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• v.31 no.2
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• pp.67-73
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• 2018

The objective of this study was to investigate the application of sulfate solvents for the economic and eco-friendly leaching of valuable metals from Au concentrate using an acid bake-water leaching system (AWS). AWS experiments were performed using an electric furnace with various baking temperatures ($100-500^{\circ}C$) and sulfate solvents ($H_2SO_4$, $K_2SO_4$, $(NH_4)_2SO_4$, $MgSO_4$, and $CaSO_4$). The efficiency of the valuable metal leaching increased as the baking temperature was increased to $400^{\circ}C$. Based on the AWS leaching time experiments, the maximum leaching rate occurred with the aqueous $(NH_4)_2SO_4$ solvent. This study demonstrates that aqueous $(NH_4)_2SO_4$ could be used as an effective solvent for valuable metal leaching using an AWS.