• Journal of the Korean Chemical Society
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• v.34 no.2
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• pp.117-122
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• 1990

The rate constants for the aquation of $trans-[CoETECl_2]^+ \;and \;cis-{\beta}-[CoTETCl_2]^+$ and the isomerization of $trans-[CoETEClOH_2]^{2+}$ were measured by spectrophotometric method under various temperature and pressure conditions. For the aquations of $trans-[CoETECl_2]^+ \;and\; cis-{\beta}-[CoTETCl_2]^+$, the activation entropies are 4.0 eu and 5.3 eu respectively and the activation volumes are $-5.8 cm^3mol-1\; and\; -6.6 cm^3mol^{-1}$ at 40$^{\circ}C$, respectively. From these data the dissociative mechanism involving trigonal bipyramid-type intermediate is proposed for the acquation reaction. For the isomerization of $trans-[CoETEClOH_2]^{2+}\; to\; cis-{\beta}-[CoETEClOH_2]^{2+}$ the activation entropy is 9.5 eu and the activation volume is $8.4 cm^3mol^{-1}(30^{\circ}C$. The mechanism of isomerization may be considered as the dissociative mechanism with $H_2O$-dissociation.

• 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 Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.1 no.1
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• pp.25-39
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• 2003

This study proposed a new electrolytic reduction technology that is based on the integration of simultaneous uranium oxide metallization and Li$_2$O electrowinning. In this electrolytic reduction reaction, electrolytically reduced Li deposits on cathode and simultaneously reacts with uranium oxides to produce uranium metal showing more than 99% conversion. For the verification of process feasibility, the experiments to obtain basic data on the metallization of uranium oxide, investigation of reaction mechanism, the characteristics of closed recycle of Li$_2$O and mass transfer were carried out. This evolutionary electrolytic reduction technology would give benefits over the conventional Li-reduction process improving economic viability such as: avoidance of handling of chemically active Li-LiCl molten salt increase of metallization yield, and simplification of process.

• Journal of the Korean Chemical Society
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• v.16 no.5
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• pp.284-289
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• 1972

Rates of the reactions of m-and p-ring-substituted thiobenzamides with benzyl bromide in acetone have been determined by an electric conductivity method. The Hammett rule has been adopted for these reactions. It has been observed that an electron-attracting substituent accelerates the reaction while an electron-donating substituent retards the reaction, and a mechanism which accounts for the observed kinetics has been postulated. The activation energies and entropies of activation for these reactions have also been calculated.

• KSBB Journal
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• v.8 no.3
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• pp.266-271
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• 1993

The effective diffusion coefficients of glucose, sucrose and fructo-oligosaccharides in Ca-alginate gel beads at high concentration of sucrose solutions were investigated at $50^{\circ}C$. A mathematical model for the kinetics of fructo-oligosaccharide production using immobilized cells was proposed and compared with experimental results varying the bead size, the substrate concentration and the bead ratio. Very low values of diffusion coefficients ranging $1.2-7.6\times10^{-7}\textrm{cm}^2$/sec were obtained, and the predicted results were in good agreement with experimental ones in all cases tested.

• Journal of the Korean Chemical Society
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• v.38 no.1
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• pp.41-49
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• 1994

Exchange reaction mechanisms of the Pb(II) ion for the complexes between Pb(II) ion and nitrogen oxygen donor macrocyclic ligands, such as 1,13-diaza-3,4 : $1011-dibenzo-59-dioxacyclohexa-decane(NtnOtnH_4)$, 1,15-diaza-3,4 : $1213-dibenzo-5811-trioxacycloheptadecane(NenOdienH_4)$, and 1,15-diaza-3,4 : $1213-dibenzo-5811-trioxacyclooctadecane(NtnOdienH_4)$, were studied by $^{207}Pb-NMR$ spectroscopy in N,N'-dimethylformamide(DMF) solutions. The associative-dissociative mechanism dominated in $NtnOtnH_4-Pb(II)$ and $NtnOdienH_4-Pb(II)$ system. For $NenOdienH_4-Pb(II)$ system, the bimolecular exchange mechanism prevailed below $-5^{\circ}C$, and both bimolecular exchange and associative-dissociative mechanism dominated above $+5^{\circ}C.$ The order of activation energies for dissociation was $NtnOdienH_4\;<\;NtnOtnH_4\;<\;NenOdienH_4$ which was reverse to the order of stabilities.

• Korean Journal of Materials Research
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• v.6 no.3
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• pp.291-296
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• 1996

Diglycidy1 ether of bisphenol A (DGEBA)/4, 4' -methylene dianiline(MDA)에 hydroquinonepheny1 glycidy1 ether(HQ-PGE)를 첨가한 계의 경화반응 메카니즘 FT-IR을 이용하여 연구하였다. 15$0^{\circ}C$에서 경화반응이 일어날 경우 반응기간이 증가할 때 에폭시기와 히드록시기는 감소하였고, 에테르기는 증가하였다. 그리고, HQ-PGE의 함량이 증가함에 따라 에폭시기의 소모량이 증가하였고, 유리 전이 온도가 감소하였다. 이로부터 HQ-PGE는 반응에 참여할 때 사슬 확장제와 반응 가속제로 작용함을 할 수 있었다.

• Journal of the Korean Chemical Society
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• v.38 no.8
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• pp.552-561
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• 1994

The cis → trans thermal isomerization of azobenzene derivatives has been studied. A sizable solvent effect on the rates for thermal isomerization of push-pull azobenzenes are observed. It is suggested that the isomerization proceeds via a rotational mechanism. For non push-pull azobenzenes, the lack of solvent effects on the rate of isomerization was observed. This suggests that the isomerization proceeds via an inversional mechanism for non push-pull azobenzenes.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2001.11a
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• pp.134-137
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• 2001

• Journal of the Korean Chemical Society
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• v.30 no.1
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• pp.40-46
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• 1986

Rate constants for the solvolysis of o-methylbenzyl chloride were determined at 30$^{\circ}$ and 40$^{\circ}$C in aqueous ethanol mixtures under various pressures up to 1600 bar. From the rate constants, the activation parameters ${\Delta}V^{\neq}$, ${\Delta}{\beta}^{\neq}$, ${\Delta}H^{\neq}$, ${\Delta}S^{\neq}$ and${\Delta}G^{\neq}$ were evaluated. The values exhibit the extremum behavior at about 0.30 mole fraction of ethanol. This behavior is discussed in terms of electrostriction. To examine the reaction mechanism by Laidler and Eyring equation, we compared the rate constants with the dielectric constants of aqueous ethanol and the number of water molecule participated in the transition state. It was concluded that solvolytic reaction proceeds via $S_N$1 mechanism.