• Journal of the Korean Chemical Society
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• v.34 no.2
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• pp.123-129
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• 1990

The rate constants for the solvolysis of $trans-[Cr(en)_2Br_2]^+$ ion were determined by the spectrophotometric method in methanol-, ethanol-, acetone-, and acetonitrile-water mixtures, at 20, 25, 30, and 35$^{\circ}C$, respectively. The rate constants increased with increasing co-solvent compositions. The rate constant did not show any relation with the reciprocal of dielectric constant of the solvent-mixtures. The m values of Grunwald-Winstein equation for methanol-, ethanol-, acetonitrile-, and acetone-water mixtures are 0.109, 0.103, 0.101, and 0.095, respectively. A free energy cycle for the process from the initial state to the transition state in water and water + co-solvent mixtures shows that the change in solvation at the transition state has a dominant effect on the rate. From the above results, it is believed that the mechanism for the aquation of this complex is the Id mechanism.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.6
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• pp.396-404
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• 2011

An investigation on the removals of PAH-quinone compounds, which are commonly produced from the biological and/or chemical treatments of PAH-contaminated soils, from the aqueous phase via birnessite (${\delta}-MnO_2$)-mediated oxidative transformation is described. It was demonstrated that acenaphthenequinone (APQ), p-PAH quinone can be removed via birnessite-mediated oxidative-coupling reactions, and anthraquinone (AQ) and 1,4-naphthoquinone (1,4-NPQ), o-PAH quinones were efficiently removed by birnessite-mediated cross-coupling reactions in the presence of catechol (CAT) as a reactive mediator. The removals of PAH-quinone compounds followed pseudo-first-order reactions, and the rate constant (k, $hr^{-1}$) for the removals of 1,4-NPQ under the experiment conditions (1,4-NPQ = 10 mg/L, CAT = 50 mg/L, ${\delta}-MnO_2$ = 1.0 g/L, pH 5, Reaction time = 6~96 hr) was 0.0426, which was about 4 times lower than that of APQ (0.173). With the observed pseudo-first order rate constants with respect to birnessite loadings under the same experimental conditions, the surface-normalized specific rate constant, $K_{surf}$, for 1,4-NPQ was determined to be $8.5{\times}10^{-4}L/m^2{\cdot}hr$. The analysis of the kinetic data with respect to birnessite loading indicated that the cross-coupling reactions of 1,4-NPQ consist of two different reaction steps over time and the results have also been discussed in terms of the reaction mechanisms.

• Journal of the Korean Chemical Society
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• v.48 no.5
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• pp.461-466
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• 2004

Kinetics for the nucleophiles have been studied under high vacuum and high pressures in various temperatures. Pseudo-first order rate constants, second order rate constants, thermodynamic parameters and Hammett ${\rho}$-values are determined. The values of ${\Delta}V^{\neq},\;{\Delta}{\beta}^{\neq}\;and\;{\Delta}S^{\neq}$are all negative. The Hammett r-values are negative for the nucleophile (${\rho}$x) over the pressure range studied. The results of kinetic studies for pressure and nucleophilet show that these reactions proceed in typical $S_N2$ reaction mechanism and change of mechanism.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.5
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• pp.535-542
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• 2006

In this study, removals of 1-naphthol by oxidative-coupling reaction using birnessite, one of natural Mn oxides present in soil, was investigated in various experimental conditions(reaction time, Mn oxide loadings, pH, etc). Removal efficiency of 1-naphthol by birnessite was high in all the experimental conditions, and UV-vis. and mass spectrometric analyses on the supernatant after reaction confirmed that the reaction products were oligomers formed by oxidative-coupling reaction. Pseudo-first order rate constants, f, for the oxidative transformation of 1-naphthol by birnessite was derived from the kinetic experiments under various amount of birnessite loadings, and using the observed pseudo-first order rate constants with respect to birnessite loadings, surface area-normalized specific rate constant, $k_{surf}$ was also determined to be $9.31{\times}10^{-4}(L/m^2{\cdot}min)$ for 1-naphthol. In addition, the oxidative transformation of 1-naphthol was found to be dependent on solution pH, and the pseudo-first order rate constants were increased from 0.129 at pH 10 to 0.187 at pH 4.

• Applied Chemistry for Engineering
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• v.9 no.6
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• pp.857-863
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• 1998

A simple and new experimental method for determination of lysozyme-M. lysodeikticus cell lysis reaction and lysozyme activity was suggested using Beer's law. The UV transmittance of the solution changed with the concentration of M. lysodeikticus and the relationship between the UV transmittance and M. lysodeikticus cell concentration followed Beer's Law. In addition, it was experimentally proven that the UV transmittance of the solution was not influenced by the lysozyme concentration and product of the lysis reaction. During the lysozyme-M. lysodeikticus cell lysis reaction, thus, M. lysodeikticus cell concentration in the solution could be measured in-situ by UV-spectrophotometer. By using these experimental data, kinetic Parameters of the Michaelis-Menten equation for the lysozyme-M. lysodeikticus cell 1ysis reaction was simply determined The maximum reaction rate constant ($k_3$) and Michaelis-Menten constants were $0.1734sec^{-1}$ and $9.83{\times}10^{-6}M$ respectively. The activity of the lysozyme could also be obtained with this experiment because the lysis reaction rate of the 1ysozyme depended on its activity.

• Korean Journal of Food Science and Technology
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• v.35 no.3
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• pp.399-404
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• 2003

Aliphatic polyester, especially poly(butylene adipate)(PBA), is quite biodegradable and one of the most promising polymer materials to be commercialized. Bis(4-hydroxybutyl) adipate (BHBA) formation stage is the first principal process in the production of PBA from adipic acid (AA) and 1,4-butane diol (BD). In this study, we investigated for the effective production of Bis(4-hydroxybutyl) adipate (BHBA), effects of molar ratio of adipic acid (AA) to 1,4-butane diol (BD), catalyst (tetrabutyl titanate, TBT) concentration, and temperature on the reaction rate of esterification between AA and BD were investigated. Initial reaction rate of the esterification decreased with increasing molar ratio of AA to BD and reaction temperature, whereas reaction constant increased with increase in catalyst-concentration. Activation energy values for catalyzed and uncatalyzed esterifications were 198.5 and 94.8 kJ/mol, respectively.

• Proceedings of the Korea Water Resources Association Conference
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• 2001.05b
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• pp.1183-1188
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• 2001

• Journal of Korea Soil Environment Society
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• v.5 no.2
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• pp.87-97
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• 2000

The effects of environmental conditions, initial dissolved oxygen concentrations, pH, and the presence of electron carrier vitamin $B_{12}$, on the reduction rate of Tn by $Fe^0$ was quantitatively analyzed using a batch reactor In all experiments, TNT reduction was best described with a first order reaction and the reduction rate decreased with the increase in the initial DO concentration. However, the specific reaction rate did not decrease linearly with the increase in the initial DO concentration. In the presence of HEPES buffer 0.2 and 2.0 mM(pH 5.7$\pm$0.2), the specific reaction rate increased more than 5.8 times, which showed reduction rate is rather significantly influenced by the pH of the solution. To test the possibility of reaction rate enhancement, well-known electron carrier(or mediator) , vitamin $B_{12}$, has augmented besides $Fe^0$. In the presence of 8.0 $mu\textrm{g}$/L of vitamin $B_{12}$, the specific reaction rate increased as much as 14.6 times. The results indicate that the addition of trace amount of vitamin $B_{12}$ can be a promising rate controlling option for the removal of organics using a $Fe^0$ filled permeable reactive barrier.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2006.11a
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• pp.469-472
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• 2006

BI 및 ETABr의 농도변화에 따른 속도상수의 변화는 이 반응이 단순한 1차 및 2차 반응 속도식에 맞지 않는다. 이와 같은 현상은 용액 속에서 두 반응 시약인 p-NPDPIN 및 BI와 상전이촉매인 ETABr 사이에 많은 수의 작은 응집된 입자(aggregates)을 형성함을 의미한다. 수용액 속에서는 불용성인 p-NPDPIN과 수용성인 BI가 충돌하여 반응할 기회가 적은데 반하여 ETABr은 이 두 시약을 함께 수용하여 세 분자 사이에 응집현상이 일어남으로 p-NPDPIN과 BI가 반응하기에 충분한 거리 내에 있게 된다. 바꾸어 말하면, 이 두 반응물질이 1:1 adducts로 반응하기보다는 여러 ETABr과 함께 많은 수의 반응분자들이 회합(응집) 되어 있음을 뜻한다.

• Journal of the Korean Chemical Society
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• v.14 no.1
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• pp.85-89
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• 1970

The rate of the bromine-exchange reaction between gallium bromide and isopropyl bromide in nitrobenzene was measured at 19$^{\circ},\;25^{\circ}$ and 40$^{\circ}C$., using isopropyl bromide labelled with Br-82. The results indicated that the exchange reaction was second order with respect to gallium bromide and first order with respect to isopropyl bromide. The third-order rate constant determined at 19$^{\circ}C$. was 3.2 ${\times}10^{-2}l^2{\cdot}mole^{-2}sec^{-1}$. The activation energy, the enthalpy of activation and the entropy of activation for the exchange reaction were also determined.