• Journal of the Korean Chemical Society
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• v.21 no.2
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• pp.83-88
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• 1977

Kinetic studies on the rates of reactions of 2, 4-dinitrochlorobenzene with p-toluidine, aniline and p-chloroaniline in $CH_3CH-CH_3OH$ binary solvent mixtures have been carried out. The experimental results have been explained in terms of the specific solvation by alcoholic hydrogen. It has been shown that the bond breaking step is rate determining in the solvent system studied and the energy barrier is getting low as the solvent changes from acetonitrile to methanol.

• Journal of the Korean Chemical Society
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• v.28 no.3
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• pp.155-162
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• 1984

Kinetic studies for the nucleophilic substitution reactions of para-substituted benzyl bromides and benzyl iodide with anilines were carried out in MeOH-MeCN mixtures at 35.0$^{\circ}$C. Hammett $ {\rho}_N,\;{\rho}_C$, Bronsted $ {\beta}$ and solvatochromic correlation coefficient a, s values were determined in order to clarify the transition state variations caused by changing nucleophiles, substituents, leaving group and solvents. The results of solvatochromic equation showed that ${\pi}^{ast}$effect was a dominant factor for the reaction systems studied. It was shown that the reaction proceeds via the dissociative $S_N$2 mechanism using the potential energy surface model approach. The potential energy surface model approach however failed to account for the transition state variation due to leaving group changes. The quatum mechanical approach showed that kinetic results were consistent with proposed dissociative $S_N$2 mechanism.

• Proceedings of the Korean Fiber Society Conference
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• 1999.04a
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• pp.16-19
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• 1999

• Journal of the Korean Chemical Society
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• v.38 no.3
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• pp.179-185
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• 1994

The Raman stretching frequency of nitrile group was affected by change of solvents and its in concentration in same solvent. In the case of acetonitrile, nitrile group stretching frequencies were observed in the region of 2247.3∼2254.9 cm-1 with various solvents. While in benzonitrile, they were found in the region of 2226.1∼2230.3$ cm^{-1}. With the addition of water in acetonitrile,νC≡N was shifted to high frequency from 2250.1 cm^{-1} in pure acetonitrile to 2257.7 cm^{-1} in 90% water forwhich had with higher volume % of water caused higher hydrogen-bonded equilibrium between methyl protons and water. The νC≡N frequency for nitrile group was shifted to high frequency by solvent inductive effect with the increasing mixed solvent (CHCl_3/CCl_4)$mole% ratio.

• Journal of the Korean Chemical Society
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• v.20 no.3
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• pp.185-192
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• 1976

Equivalent conductances of ammonium salts such as $NH_4Cl,\;CH_3NH_3Cl,\;(CH_3)_2NH_2Cl,\;(CH_3)_3NHCl\;and\;(CH_3)_4NCl$ have been measured in methanol-water mixtures of various composition (0.0${\sim}$0.6-mole frcation: m. f.) in the concentration range from 0.01 to 0.04 M at $25^{\circ}C$, and limiting equivalent conductances (${\Lambda}_0$) are determined by the analysis of Fuoss Onsager's semiempirical equation.The experimental results are discussed in terms of varing the size of ${\Lambda}_0$ due to the salts species and solvent composition. It has been observed in quite common over all salts that ${\Lambda}_0$ decreases with the increase of m. f. methanol, and the maximum decrement in ${\Lambda}_0$ shows between water and 0.1 m. f., while the plot of ${\Lambda}_0$ vs. m. f. goes through a minimum at 0.4 m. f. and then turns slightly upward. On the other hand, the ${\Lambda}_0$ decrease with the increase of the size of ammonium cation and the larger values ${\Lambda}_0$ are showed in comparison with those of values observed for the corresponding $n-RNH_3Cl$ under the same experimental procedure. All these behaviors are considered to be closely correlated with the structures of solvents and solutes and the significant similarities are compared with the behaviors of partial molar volumes for amine salts in same solvent system.

• Journal of the Korean Chemical Society
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• v.25 no.3
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• pp.152-159
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• 1981

The rates of solvolysis for p-nitrobenzyl chloride have been measured by the electric conductivity method in aqueous ethanol from 0.0 to 0. 5 mole fraction of ethanol under various pressures up to 1200bar at 50 and $60{\circ}C$. The activation parameters, ${\Delta}V_\0^{\neq},\ {\Delta}H^{\neq}$ and ${\Delta}S^{\neq}$ are evaluated from the rate constants. The results indicated that ${\Delta}V_\0^{\neq}$ exhibits an extremum behaviors near 0.3 mole fraction of ethanol and ${\Delta}H^{\neq}$ and ${\Delta}S^{\neq}$ near 0.1 mole fraction of ethanol. This behaviors are discussed in terms of solvent structure variation and the pressure dependences of ${\Delta}H^{\neq},\ {\Delta}H^{\neq}$ and ${\Delta}S^{\neq}$ are also discussed individually. The signs of the pressure dependence of ${\Delta}H^{\neq}$${\Delta}S^{\neq}$ are shown to be consistent with those required by the Maxwell relationships for classical thermodynamic systems.

• Journal of the Korean Chemical Society
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• v.24 no.4
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• pp.288-294
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• 1980

Methanolysis rate constants were determined for $CH_3O(CO)Cl,\;CH_3S(CO)Cl\;and\;CH_3S(CS)Cl\;in\;CH_3OH-CH_3CN$ mixtures. Results show that the rates are not predominantly influenced by the bulk solvent properties but are partly influenced by specific electrophilic solvation.Polarity of the solvent is not a dominant factor but it nevertheless plays a role in charge stabilization of the $S_N1$ like transition state. The methanolysis proceeds through $S_N1$ mechanism for $CH_3S(CS)Cl$ for which both specific solvation of leaving group by methanol and charge stabilization by a high dielectric medium are important, while for $CH_3O(CO)Cl\;methanolysis occurs\;via\;S_N2$ mechanism in which both of the solvent effects are unimportant.

• Korean Chemical Engineering Research
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• v.46 no.5
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• pp.965-970
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• 2008

The separation of sulfone components using light cycle oil(LCO) after oxidation was carried out by solvent extraction method using various polar solvents such as water, n-methyl-2-pyrrolidone(NMP), dimethyl sulfoxide, ethyl acetate, acetonitrile, dimethyl formamide, and methyl alcohol. It was found that phase separation between LCO layer and solvent occurred under mixed solvent adding a proper amount of water. The mixture solvent of NMP and water was a promising extraction solvent due to the selective removal and high distribution coefficient of sulfone component in LCO. 99.5% over of sulfur contents in LCO can be removed by 4 stages equilibrium extraction.

• Food Science and Preservation
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• v.9 no.3
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• pp.332-337
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• 2002

This study was undertaken in order to compare reflux extraction(RE) and microwave-assisted extraction(MAE) in extraction efficiency and establish optimum microwave extraction conditions in obtaining Ligularia fischeri extracts. A considerable reduction in extraction time was accomplished by MAE. When 70% methanol 50% methanol 70% ethanol, or 50% ethanol was used, MAE extract contained equal levels of soluble solid and total polyphenol as obtained by RE. The optimum microwave-assisted extraction conditions for Ligularia fischeri were achieved by 120∼150 watts of microwave energy and 4∼8 minutes of extraction time. No significant changes were found in antioxidant activity with DPPH scavenging method over the variation of microwave energy or extraction time. The use of diluted methanol or ethanol improved soluble solid content(30%), total polyphenol content(2.7%) and antioxidant activity(68%).

• Journal of the Korean Chemical Society
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• v.27 no.2
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• pp.95-101
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• 1983

The pseudo-first order rate constants have been obtained for the solvolysis of benzoyl cyanide in various aqueous solvent mixtures and ethanol-trifluoroethanol mixtures at 1, 5, 10, 15 and $20^{\circ}C$. Values of n in the Kivinen polt, m values of Grunwald-Winstein polt, $\beta$ values of Leffler relationship and values of m and l in the extended Grunwald-Winstein polt have been calculated and studied the transition state variation caused by solvent changes using the More O'Ferrall polt and quantum mechanical approach. It has been shown that the reaction proceed via the associative $S_N2$ mechanism, using the transition state parameters and quantum mechanical model approach.