• Bulletin of the Korean Chemical Society
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• v.6 no.3
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• pp.162-164
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• 1985

Nucleophilic substitution reaction of dansyl chloride with anilines in various solvents have been investigated. The Bronsted ${\beta}$ and Hammett ${\rho}_N$ values indicated that the bond formation is advanced more than the bond breaking at the transition state. Solvatochromic correlations also predicted the importance of bond formation at the TS, showing a greater contribution of polarity (${\pi}^{\ast}$) compared to hydrogen bond donor acidity (${\alpha}$). The effect of solvent on rate was found to violate the reactivity-selectivity principle.

• 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.

• Ocean and Polar Research
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• v.39 no.2
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• pp.115-124
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• 2017

The objective of this study is to evaluate the antioxidant activity of the fruits of Ligustrum japonicum. The crude extract was successively fractionated into n-hexane, 85% aqueous methanol (85% aq.MeOH), n-butanol (n-BuOH), and water fractions by means of solvent polarity. The crude extract and its solvent fractions were evaluated for their antioxidant effect by four different assay systems: scavenging power on peroxynitrite and intralcellular ROS produced in HT-1080 cells; DNA oxidation inhibition; ferric reducing antioxidant power (FRAP). The n-BuOH fraction exhibiting potent antioxidant activity was further purified by C18 silica gel column chromatography and RP-HPLC to give tyrosol (1) and salidroside (2). The structure of isolated compounds was determined by extensive 2 D NMR experiments such as $^1H$ COSY, NOESY, HSQC and HMBC as well as by comparison with the published spectral data.

• Bulletin of the Korean Chemical Society
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• v.8 no.4
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• pp.341-344
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• 1987

The fluorescence quantum yield of khellin is sensitive to temperature and to the nature of solvents, especially the proton-donating ability in solute-to-solvent hydrogen bonding. The intersystem crossing quantum yields are 0.4 and 0.15 in acetonitrile and ethanol, respectively. The fluorescence quantum yields in ethanol and isopentane at 77 K are 0.61 and 0.07, respectively, both of which are much larger than the values at room temperature. The phosphorescence lifetime is relatively long and decreases with decreasing solvent polarity. The phosphorescence to fluorescence quantum yield ratio is very small and remains unchanged in various solvents. The results suggest that internal conversion is an important decay channel of the excited singlet state of khellin, especially in the hydrogen-bonding hydroxyl solvents.

• Journal of the Korean Chemical Society
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• v.30 no.1
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• pp.3-8
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• 1986

The investigation of the effect of solvent structure on the first-order solvolysis of cis-$[Co(en)_2ClNO_2]^+$ion has been extended to water + co-solvent mixtures where the co-solvents are glycerol, ethylene glycol, isopropyl alcohol and t-butyl alcohol. Rates of solvolysis have been evaluated by spectrophotometric method at temperature 25∼30$^{\circ}$C. The polarity of solvent has influence on the variation of rate constant. The non-linear plot of the rate constant in log scale versus $\frac{D-1}{2D+1}$ implies that change in solvent structure with composition plays an important role in determining the variation of rate constant. The linearity of the plot of the rate constant in log scale versus the Grundwald-Winstein Y factor confirms that the solvolysis is an Id-type process with considerable extension of the metal chloride bond in the transition state. In the Kivinen equation the slope of the plot of log k versus $log(H_2O)$ suggests that the solvolysis is also an Id-type process. The application of free energy cycle shows that the effect of solvent structure is greater in the transition state than in the initial state.

• Applied Chemistry for Engineering
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• v.5 no.4
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• pp.646-656
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• 1994

The ${\omega}$-formyl carboxylic acid was produced by ozone oxidation of cycloolefins in the presence of pyridine and its production yield was examined by varying temperature and solvent. As the reaction temperature increased, the yield of ${\alpha}$, ${\omega}$-dicarboxylic acid increased whereas that of ${\alpha}$, ${\omega}$-dialdehyde decreased. As the polarity of solvent increased, a higher yield of desired ${\omega}$-formyl carboxylic acid was obtained, whereas the yield of unwanted polymeric ozonide decreased. The yields of ${\omega}$-formyl carboxylic acid from ozone oxidation of cyclohexene, cyclooctene and cyclododecene at $0^{\circ}C$ and in methylene chloride solvent were 59.30%, 55.20%, and 36.72%, respectively.

• Journal of the Korean Chemical Society
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• v.33 no.5
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• pp.538-544
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• 1989

The increase of B-type hydrogen bonding character between the hydrogen atom($H{\gamma}$) of methylene group in 1-(phenoxymethyl)benzotriazole (1) and 1-(thiophenoxymetyl)benzotriazole (2) derivatives, and solvents was caused by some factors such as;electron withdrawing strength (${\rho} > 0$) of X-substituent; local diamagnetic effect by Y atom (Y = O(1) > S(2)) with adjacent methylene group; and solvent polarity parameter ($E_T$ = Kcal/mol; acetone; 42.2 > chloroform; 39.0). From the basis on the findings, linear free energy relationship (LFER) components on the substituent chemical shift of methylene group ($CH_2-SCS$) in (1) exhibited a tendency that resonance(R)-effect was much larger than field(F) (or inductive(I))-effect in acetone and that the electrical effects were depend upon the solvent.

• Journal of the Korean Chemical Society
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• v.37 no.3
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• pp.335-343
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• 1993

The maximum absorption wavelengths of charge-transfer complexes of naphthalene, ${\alpha}-and{\beta}-methyl$ naphthalene and 1,2-, 2,3-and 2,6-dimethyl naphthalene with chloranil have been measured with a UV spectrophotometer in ethylene chloride, methylene chloride, and chloroform at 10, 15, 20, and 25$^{\circ}C$. This absorption band was interpreted as the charge transfer band of a 1 : 1 molecular complex, and the maximum absorption wavelength was changed as a function of solvent and temperature. Their formation constants (K$_f$) were decreased with the polarity of solvent and the increase of temperature. Thus, the influences of solvent and temperature on the formation constant have been discussed as consideration of thermodynamic properties, and the electronic and steric effects of electron donors on formation constant have been also discussed.

• Journal of the Korean Chemical Society
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• v.32 no.2
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• pp.85-93
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• 1988

Solvolyses of t-butylhalides (X = Cl, Br, I) in quasi isodielectric solvent system, MeOH-nitromethane, MeOH-nitrobenzene and MeOH-ethyleneglycol have been studied kinetically. Methanolyses for t-butylhalides in MeOH-NM and MeOH-NB show rate maxima at 40~100 % (v/v) MeOH. The rate maxima observed have been interpreted as a result of cooperative enhancement of polarity-polarizability and hydrogen bonddonor ability of solvents. The influences of polarity-polarizability and hydrogen bonddonor ability on reactivities of substrates have been discussed in terms of Y value changes. The solvolysis rates for t-butylhalides in E.G. are more than 20 fold faster than those in MeOH and this was attributed to the solvent structure of E.G.