• 대한화학회지
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• 제18권4호
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• pp.251-258
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• 1974

아세톤, 아세토니트릴, 메탄올, 에탄올 등의 용매에서 치환염 벤조일과 파라니트로아닐린과의 친핵치환반응에 대한 속도상수를 전기 전도도법으로 구하고 활성화 파라미터를 계산하였다. 결과로 반양성자 용매보다는 양성자성 용매에서 반응속도가 빨랐고 같은 성질의 용매에서는 유전상수가 큰 쪽이 반응이 더 빨랐으며 각 용매에 있어서의 Hammett도시는 정의 기울기를 가진 직선을 나타내었으며, 반응은 첨가-제거 메카니즘으로 일어났다.

• Bulletin of the Korean Chemical Society
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• 제6권5호
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• pp.259-263
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• 1985

Rate Constants for the solvolysis of p-methylbenzyl chloride in various ethanol-water mixtures were studied at 30 and $40^{\circ}C$ under various pressures up to 1600 bar. The rates of reaction were increased with increasing temperature and pressure, and decreased with increasing solvent composition of ethanol mole fraction. From the rate constants, the values of the activation parameters (${\Delta}V^{\neq},{\Delta}{\beta}^{\neq},{\Delta}H^{\neq}\;and\;{\Delta}S^{\neq}$) were evaluated. The values of ${\Delta}V^{\neq}\;and\;{\Delta}{\beta}^{\neq}$ exhibit the extremum behavior at about 0.30 mole fraction of ethanol. This behavior is discussed in terms of solvent structure variation (electrostriction). From the relation between the reaction rate and the dielectric constant of solvent or the number of water molecule participated in the transition state, it could be postulated that the reaction proceeds through $S_N1$ mechanism.

• 한국응용과학기술학회지
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• 제18권2호
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• pp.103-110
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• 2001

Resource recovery and recycling of materials and products, including polyurethanes is viewed as a necessity in today's society. Most urethane polymers are made from a polyol and a diisocyanate. these and be chemicals such as water, diamines or diols that react with isocyanate groups and add to the polymer backbone. The problems of recycling polyurethane wastes has major technological, economic and ecological significance because polyurethane itself is relatively expensive and its disposal whether by burning is also costly. In general, the recycling methods for polyurethane could be classified as mechanical, chemical and feedstock. In the chemical recycling method, there are hydrolysis, glycolysis, pyrolysis and aminolysis. This study, the work was carried out glycolysis using sonication ant catalyzed reaction. Different kinds of recycled polyols were produced by current method(glycolysis), catalyzed reaction and sonication as decomposers and the chemical properties were analyzed. The reaction results in the formation of polyester urethane diols, the OH value which is determined by the quantity of diol used for the glycolysis conditions. The glycolysis rates by sonication for the various glycols, increased as fallows: PPG

• Bulletin of the Korean Chemical Society
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• 제32권3호
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• pp.964-972
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• 2011

This work investigated the difference between $Fe^{2+}$ autoxidation-induced and Fenton-type cleavage of pBR322 plasmid DNA. $^{\cdot}OH$ generation reactions in the absence and presence of $H_2O_2$ under various conditions were also investigated. Although both the $Fe^{2+}$ autoxidation and Fenton-type reactions showed DNA cleavage and $^{\cdot}OH$ generation, there were significant differences in their efficiencies and reaction rates. The rate and efficiency of the cleavage reaction were higher in the absence of 1.0 mM of $H_2O_2$ than in its presence in 20 mM phosphate buffer. In contrast, the $^{\cdot}OH$ generation reaction was more prominent in the presence of $H_2O_2$ and showed a pH-independent, fast initial reaction rate, but the rate was decreased in the absence of $H_2O_2$ at across the entire tested pH range. Studies using radical scavengers on DNA cleavage and $^{\cdot}OH$ generation reactions in both the absence and presence of $H_2O_2$ confirmed that both reactions spontaneously involved the active oxygen species $^{\cdot}OH$, ${O_2}^{\cdot-}$, $^1O_2$ and $H_2O_2$, indicating that a similar process may participate in both reactions. Based on the above observations, a new mechanism for the $Fe^{2+}$ autoxidation-induced DNA cleavage reaction is proposed.

• 한국응용과학기술학회지
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• 제26권4호
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• pp.415-421
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• 2009

Esterification reaction between succinic acid[SA] and 1,4-butanediol [BD} was kinetically investigated in the presence of organic metal catalysts (alkyl-silver oxide(ASO),CAT 100E) at $150{\sim}190^{\circ}C$. The reaction rates measured by the amount of distilled water from the reaction vessel. The esterification reaction was carried out under the first order kinetics with respect to the concentration of reactants and catalyst, respectively. The overall reaction order was 2nd. From the examination of relationship between apparent reaction rate constants and reciprocal absolute temperature, the activation energy has been calculate as 146.70 kJ/mol with ASO catalyst and 43.04 kJ/mol with CAT 100E catalyst.

• Korean Chemical Engineering Research
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• 제59권1호
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• pp.138-151
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• 2021

The effect of a reactant ratio on the growth of a buoyancy-driven instability in an irreversible A+B→C reaction system is analyzed theoretically and numerically. Taking a non-stoichiometric reactant ratio into account, new linear stability equations are derived without the quasi-steady state assumption (QSSA) and solved analytically. It is found that the main parameters to explain the present system are the Damköhler number, the dimensionless density difference of chemical species and the ratio of reactants. The present initial grow rate analysis without QSSA shows that the system is initially unconditionally stable regardless of the parameter values; however, the previous initial growth rate analysis based on the QSSA predicted the system is unstable if the system is physically unstable. For time evolving cases, the present growth rates obtained from the spectral analysis and pseudo-spectral method support each other, but quite differently from that obtained under the conventional QSSA. Adopting the result of the linear stability analysis as an initial condition, fully nonlinear direct numerical simulations are conducted. Both the linear analysis and the nonlinear simulation show that the reactant ratio plays an important role in the onset and the growth of the instability motion.

• Bulletin of the Korean Chemical Society
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• 제13권1호
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• pp.65-70
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• 1992

The hindered internal rotation effect of methyl group on chemical reaction was studied for cis-trans isomerization reaction of 1-bromopropene system using RRKM technique. A comparative study of the isomerization rates was also performed between the rigid and allowed internal rotations. The calculated rate of rigid cis-trans isomerization of 1-bromopropene was shown to be three times higher than its other halogenated propene homologues with its internal rotations and found to be in good agreement with experimental observations. These findings could be explained reasonably well in terms of the differences of the rotational barrier heights among halogenated propenes and correlated with the relatively low internal rotation barrier of cis-1-bromopropene, 230 cal/mol, compared to those of other cis-1-halopropenes, 700-800 cal/mol, and trans-1-halopropenes, 2.0-2.4 kcal/mol.

• 한국수소및신에너지학회논문집
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• 제21권3호
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• pp.158-166
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• 2010

The purification of two liquid phases ($H_2SO_4$ phase and HIx phase) formed from a Bunsen reaction in Sulfur-Iodine (SI) hydrogen production process was investigated in order to operate SI process efficiently. The each synthetic solution for two liquid phases contained impurities was prepared on the basis of a proper composition obtained from Bunsen reaction. The purification of each solution was performed by counter-current flow using a packed column at different temperatures and $N_2$ flow rates. As the results of purification, impurities existed in each phase were decreased with increasing the temperature and the $N_2$ flow rate. In particular, the increase of the $N_2$ flow rate at the lower temperatures was effective to remove impurities by a reverse Bunsen reaction without side reactions. On the whole, it may be concluded that the purification of each phase is accomplished by mixing effects of the stripping, the evaporation, and the reverse Bunsen reaction.

• Bulletin of the Korean Chemical Society
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• 제23권10호
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• pp.1445-1450
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• 2002

Solvolytic rate constants at 25 $^{\circ}C$ are reported for solvolysis of chlorodithioformate (1) in binary mixtures of water with acetone, ethanol, methanol, methanol-d, 50%methanol-d/50%D2O, and 2,2,2-trifluroethanol (TFE), and also in TFE-ethanol mixtures. The Grunwald-Winstein plot shows that the three aqueous mixtures exhibit dispersions into separate line. The correlation is improved only slightly by additional parameters NT for solvent nucleophilicity and/or I for aromatic ring parameter. Rate ratios in solvents of the same $Y_cl$ value, having different nucleophilicity provide measures of the minimum extent of nucleophilic solvent assistance, and the value of 3.35 for $[$k_{40EW}$/$k_97TFE$]_Y$ (EW = ethanol-water), is consistent with an essentially SN1 reaction mechanism. This study has shown that the magnitude of l, m and h values associated with a change of solvent composition is able to predict the SN1 reaction mechanism. log(k/$k_o$) = mY + lN + hI

• 한국결정성장학회지
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• 제9권1호
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• pp.119-125
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• 1999

본 연구는 싸이클론 반응로에서 $FeS_{2}$의 반응 특성에 관한 조사를 연구하였다. 수학적인 모형도로 이 반응로에서 $FeS_{2}$의 oxidation과 suifation 등을 전개하엿다. 모형은 $FeS_{2}$에서 chemical control shrinking core로서 그리고 ${Ca(OH)}_{2}$에서 fluid film control shrinking core로서 가정하였으며 수식으로서 발전시켰다. 본 실험은 이 반응 파라메터들의 영향에 연구로서 진행하였으며 즉 반응로의 온도변화, $FeS_{2}$의 입자크기, 공기 주입비율, 시료 주입비율, 그리고 $FeS_{2}$와 ${Ca(OH)}_{2}$ 비율 등이다. Oxidation과 Sulfation에 의한 반응물들은 화학적 및 물리적으로 특성을 기술하였다.