• Journal of the Korean Chemical Society
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• v.53 no.1
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• pp.51-61
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• 2009

The purposes of this study are to analyze the learning contents on the measurement of reaction rate which is introduced in the high school ‘science’ and ‘chemistry II’ textbooks, and to revise the experiment appropriate to the learning contents. We examined 11 kinds of ‘science’ textbooks, 8 kinds of ‘chemistry II’ textbooks and 11 kinds of teacher’s manuals used in Korea and additionally surveyed teachers’ opinions on this subject. Most of textbook and teacher’s manuals described that ‘the reaction rate generally decreases through the time’, teachers’ conception also agreed with it. But most of experimental activities in the textbooks were inadequate to explain the concept that the reaction rate generally decreases with time. We analyzed the reasons and revised the experimental condition to solve this disagreement between the description in textbooks and an experimental result. Then we compared improved experimental result and theoretical prediction data. The improved experiment in this study is expected to help to describe the conception of chemical reaction rate in the textbook more clearly.

• Journal of the Korean Chemical Society
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• v.22 no.3
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• pp.150-157
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• 1978

The rate constants for the hydrolysis of the derivatives of N-(p-nitrophenyl)-benzohydrazonyl azide (p-$CH_3,\;p-CH_3O,\;p-NO_2$, p-Cl, p-Br) have been determined by UV spectrophotometry in 50% dioxane-water at $25^{\cicr}C$ and a rate equation which can be applied over wide pH range was obtained. Below pH 5, the rate of hydrolysis of hydrazonyl azides is accelerated by electron-donating group ($\rho$ = -0.47), whereas at the pH values greater than 7, the $\rho$-value is 0.68. The effect of salt, solvent, substituent and azide ion on the rate of hydrolysis are rationalized in terms of $S_N1$ and $S_N2$ mechanism; below pH 5, the hydrolysis proceed through $S_N1$, however, above pH 7, the hydrolysis is started by the attack of hydroxide ion and in the range of pH 5∼7, these two reactions occur competitively.

• 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.

• 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.

• Journal of the Korean Chemical Society
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• v.41 no.4
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• pp.198-204
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• 1997

The rate constants for the hydrolysis of N-(2,4-dinitrophenyl)benzhydrazonyl bromide and its derivatives were determined by ultraviolet visible spectrophotometry at 20$^{\circ}C$ and a rate equation which could be applied over a wide pH range was obtained. On the basis of rate equations derived and judging from the solvent effect, substituent effect, salt effect, thermodynamic parameter, plausible mechanisms of hydrolysis have been proposed. It may be concluded that the hydrolysis through SN1 mechanism via carbonium ion intermdiate to pH 3.0, and pH 10.0, the hydrolysis proceeds through 1,3-dipolar or SN2 mechanism.

• Journal of the Korean Chemical Society
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• v.32 no.1
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• pp.48-52
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• 1988

Kinetics of the reaction of 2-phenethyl p-bromobenzenesulfonate with substituted pyridines in acetonitrile were investigated by an electric conductivity method at 1-2000 bars and $45{\sim}55{\circ}C$. The rates of these reactions were increased with raising temperatures, pressures and by changing electron-donating substitutents in pyridine. When raising pressure the Hammett reaction parameter $I{\rho}I$ and Bronsted ${\beta}$ values were increased, and isokinetic temperature observed from isokinetic relations hip between ${\Delta}H^{\neq}$ and TEX>${\Delta}S^{\neq}$ was decreased. These results indicate that the $S_N2$ characters were increased with raising pressure.

• Journal of the Korean Chemical Society
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• v.17 no.2
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• pp.130-135
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• 1973

The rate-constants of hydrolysis of 3, 4-methylenedioxyphenylmethylenemalononitrile are determined by ultraviolet spectrophotometry at various pH and a rate equation which can be applied over wide pH range is obtained. The rate equation reveals that below pH 5.0 and above pH 9.0, the hydrolysis is initiated by the addition of water and hydroxide ion respectively. However, at pH 6.0-8.0 the competitive addition of water and hydroxide ion occurs. The catalytic contribution of hydroxide ion and water can be fully explained by the rate equation obtained.

• Applied Chemistry for Engineering
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• v.22 no.6
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• pp.718-722
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• 2011

2,4'-Bipyridinium dichromate [$(C_{10}H_8N_2H)_2Cr_2O_7$] was synthesized by the reaction of 2,4'-bipyridinie with chromium trioxide in $H_2O$. The structure was characterized by IR and ICP analysis. The oxidation of benzyl alcohol using 2,4'-bipyridinium dichromate in various solvents showed that the reactivity increased with the increase in the order of the dielectric constant (${\varepsilon}$), in the order : cyclohexene < chloroform < acetone < N,N'-dimethylformamide. In the presence of hydrochloric acid, 2,4'-bipyridinium dichromate effectively oxidized benzyl alcohol and its derivatives ($p-CH_3$, H, m-Br, $m-NO_2$) in N,N'-dimethylformamide. Electron-donating substituents accelerated the reaction, whereas electron acceptor groups retarded the reaction. The Hammett reaction constant (${\rho}$) was -0.65 at 303 K. The observed experimental data was used to rationalize the hydride ion transfer in the rate-determining step.

• Applied Chemistry for Engineering
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• v.2 no.1
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• pp.64-69
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• 1991

A lipid containing a 1, 2-dithiolane group was synthesized, and polymerized vesicle was prepared from the vesicle of this lipid by ring-opening polymerization. Reaction rate of the polymerization was monitored by UV absorption, and the results showed that it followed the first order kinetics and the rate constant $3.84{\times}10^{-2}min^{-1}$. Permeation rate of sucrose through the polymerized vesicle was $4.7{\times}10^{-8}cm\;hr^{-1}$, which is 1.5 times lower than that of monomeric analog.

• BT NEWS
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• v.11 no.2
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• pp.24-34
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• 2004

센서란 측정 대상물로부터 정보를 검지 또는 측정하여 그 측정량을 인식 가능한 유용한 신호로 변화하는 장치(device)로 정의할 수 있으며, 바이오센서(biosensor)는 생물학적 요소와분석 대상 물질과의 반응에서 나타나는 전기화학적 변화, 열에너지의 변화, 형광 또는 색의 변화 등을 인식 가능한 신호로 변환시켜 주는 장치와 결합하여 제작한 기구를 지칭한다. 바이오센서의 효시는 1962년 포도당을 측정하기 위해 Clark이 dialysis membrane을 이용하여 최초의 Glucose센서를 개발한 이래로 생물공학, 화학공학, 전자공학, 생명공학 및 컴퓨터 공학 등 여러 분야가 접목되면서 급속도로 연구 개발되어 왔다.(중략)