• Bulletin of the Korean Chemical Society
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• v.19 no.6
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• pp.671-676
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• 1998

The formation and dissociation rates of $Ce^{3+}$ Complexes of the 1,4,7,10-tetraaza-13,16-dioxacyclooctadecane-NN', N",N"'-tetraacetic acid (1), 1,4,7,10-tetraaza-13,16-dioxacyclooctadecane-N,N',N",N"'-tetramethylacetic acid (2), and 1,4,7,10-tetraaza-13,16-dioxacyclooctadecane-N,N',N",N"'-tetrapropionic acid (3) have been measured by the use of stopped-flow spectrophotometry. Observations were made at 25.0±0.1 ℃ and at an ionic strength of 0.10 M $NaClO_4$. The complexation of $Ce^{3+}$ ion with 1 and 2 proceeds through the formation of an intermediate complex $(CeH_3L^{2+})^*$ in which the $Ce^{3+}$ ion is incompletely coordinated. This may then lead to be a final product in the rate-determining step. Between pH 4.76 and 5.76, the diprotonated $(H_2L^{2-})$ from is revealed to be a kinetically active species despite of its low concentration. The stability constants $(logK(CeH_3L^{2+}))$ and specific water-assisted rate constants $(k_{OH})$ of intermediate complexes have been determined from the kinetic data. The dissociation reactions of $Ce^{3+}$ complexes of 1, 2, and 3 were investigated with $Cu^{2+}$, ions as a scavenger in acetate buffer. All complexes exhibit acid-independent and acid-catalyzed contributions. The effect of buffer and $Cu^{2+}$ concentration on the dissociation rate has also been investigated. The ligand effect on the dissociation rate of $Ce^{3+}$ complexes is discussed in terms of the side-pendant arms and the chelate ring sizes of the ligands.

• Bulletin of the Korean Chemical Society
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• v.27 no.6
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• pp.886-892
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• 2006

The interaction between tetraethylammonium chloride (TEACl) with ICl and tetraethylammonium iodide (TEAI) and aza-15-crown-5 (A15C5) with $I_2$ and ICl have been examined spectrophotometrically in acetonitrile solution. The results of TEACl-ICl indicate the formation of $ICl_2$ - through equilibrium reaction. In the case of TEAI-$I_2$ and A15C5-$I_2$, the equilibrium formation of $I_3$ - is confirmed. The interaction of TEAI-ICl begins with the simultaneous production of $I_2$ and IC$I_2$ - (at TEAI/ICl < 0.5) as well as continues with the simultaneous consumption of $I_2$ and formation of I$I_3$ - (at TEAI/ICl > 0.5). Similar behavior is also observed for A15C5-ICl system. However, the changes are seen at A15C5/ICl mole ratios less and more than 0.66. Several equations have been suggested for the formation of detected species. The formation constants of various reactions were evaluated from the computer fitting of the absorbance-mole ratio data. IR spectra of A15C5 and 1:1 A15C5:ICl or A15C5:$I_2$ complexes are compared and the effect of complexation on absorption bands is discussed.

• Bulletin of the Korean Chemical Society
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• v.35 no.6
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• pp.1749-1753
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• 2014

Pseudo-first-order rate constants ($k_{obsd}$) have been measured spectrophotometrically for the nucleophilic substitution reaction of Y-substituted-phenyl picolinates (7a-f) with potassium ethoxide (EtOK) in anhydrous ethanol at $25.0{\pm}0.1^{\circ}C$. The plot of $k_{obsd}$ vs. [EtOK] curves upward while the plot of $k_{obsd}/[EtO^-]_{eq}$ vs. $[EtO^-]_{eq}$ is linear with a positive intercept in all cases. Dissection of $k_{obsd}$ into $k_{EtO^-}$ and $k_{EtOK}$ (i.e., the second-order rate constants for the reactions with the dissociated $EtO^-$ ion and ion-paired EtOK, respectively) has revealed that the ion-paired EtOK is more reactive than the dissociated $EtO^-$. The ${\sigma}^{\circ}$ constants result in a much better Hammett correlation than ${\sigma}^-$ constants, indicating that the reaction proceeds through a stepwise mechanism in which departure of the leaving group occurs after the rate-determining step (RDS). $K^+$ ion catalyzes the reaction by increasing the electrophilicity of the reaction center through formation of a cyclic transition state (TS). The catalytic effect decreases as the substituent Y becomes a stronger electron-withdrawing group (EWG). Development of a positive charge on the N atom of the picolinyl moiety through resonance interactions is responsible for the decreasing $K^+$ ion catalysis.

• Journal of Korean Society on Water Environment
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• v.22 no.5
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• pp.958-967
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• 2006

The overall objective of this research was to find out the role of rapid mixing conditions in the species of hydrolyzed Al(III) formed by Al(III) coagulants and to evaluate the distribution of hydrolyzed Al(III) species by coagulant dose and coagulation pH. When an Al(III) salt was added to water, monomers, polymers and solid precipitates may form. Different Al(III) coagulants (alum and PSOM) show to have different Al(III) species distribution over a rapid mixing condition. During the rapid mixing period, for alum, formation of dissolved AI(III) (monomer and polymer) increases, but for PSOM, precipitates of $Al(OH)_{3(S)}$ increases rapidly. During the rapid mixing period, for high coagulant dose, Al-ferron reaction increases rapidly. The kinetic constants, Ka and Kb, derived from AI-ferron reaction. The kinetic constants followed very well the defined tendencies for coagulation condition. For pure water, when the rapid mixing time increased, the kinetic constants, Ka and Kb showed lower values. Also, for raw water, when the rapid mixing time increased, the kinetic constants, Ka and Kb showed lower values. At A/D(Adsorption and Destabilization) and sweep condition, both $Al(OH)_{3(S)}$ and dissolved Al(III) (monomer and polymer) exist, concurrent reactions by both mechanism appear to cause simultaneous precipitation.

• Journal of the Korean Chemical Society
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• v.36 no.2
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• pp.191-196
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• 1992

Reaction of N,N-dimethylaniline(N,N-DMA) and iodine in $CHCl_3,\;CH_2Cl_2 : CHCl_3$(1:1), $CH_2Cl_2$(1:1), and CH2Cl2 has been studied kinetically by using conductivity method. Pseudo first-order rate constants ($k_{obs}$) and second-order rate constants ($k_{obs}$/[N,N-DMA]) are dependent on the N,N-DMA concentration. Second-order rate constants obtained were decreased with increasing N,N-DMA concentration. We analysed these results on the basis of formation of charge transfer complex as a reaction intermediate. From the construction of reaction scheme and activation parameters for the formation and transformation of charge transfer complex. The equilibrium constants decreased when the dielectric constant of solvent was increased, and the value is 1.9${\sim}$4.2$M^{-1}$. The rate of transformation are markedly affected by the solvent polarity.${\Delta}H^{\neq}$ is 6.3-12.6kJ/mol, and ${\Delta}S^{\neq}$ is large negative value of -234J/mol K.

• Bulletin of the Korean Chemical Society
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• v.32 no.9
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• pp.3233-3238
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• 2011

The fluorescence of norfloxacin was quenched by various nucleotides. The ratio of the fluorescence intensities in the absence and presence of nucleotide was linearly dependent on nucleotide concentration, suggesting that quenching occurred through the formation of nonfluorescent norfloxacin-nucleotide complexes. The gradient of the linear relationship represented the equilibrium constant of complex formation; it decreased with increasing temperature. The slopes of van't Hoff plots constructed from the temperature-dependent equilibrium constants were positive in all cases, indicating that complex formation was energetically favorable - i.e., exothermic, with negative Gibb's free energy. The equilibrium constant increased when triphosphate was used instead of monophosphate. It also increased when the oxygen at the $C'_2$ position of the nucleotide was removed. Both enhancements were due to entropic effects: entropy decreased when complexes with AMP or GMP formed, while it increased when norfloxacin complexed with ATP, GTP, dAMP and dGMP.

• Proceedings of the KIEE Conference
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• 1989.11a
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• pp.505-508
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• 1989

A computer simulation code of UV preionized discharge KrF laser is developed, including time dependent circuit equations, boltzmann equations, and plasma kinetic equations for various atomic and molecular species. Rate constants for electron collision processes are calculated with a boltzmann equations as a function of E/N. In this study, we studied mainly the $KrF^*$ formation process, relaxation process, and the 248nm absorption process as a function of charging voltage.

• Journal of the Korean Chemical Society
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• v.44 no.3
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• pp.298-301
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• 2000

• Transactions on Electrical and Electronic Materials
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• v.4 no.1
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• pp.11-14
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• 2003

The regularities of immobilization of natural medicinal substances - alchidine on gels of poly(vinyl alcohol) - are investigated. It is shown that the polymer components of alchidine interact with nonionic polymer with formation of interpolymer complexes. The influence of the different factors on the properties of complexes is considered and the constants of alchidine distribution in the system gel - water are calculated.

• Journal of the Korean Chemical Society
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• v.14 no.1
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• pp.13-18
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• 1970

非水溶液 Ethylenediamine 中에서 水銀電極의 標準電位 및 水銀鹽化物, $HgCl_2,\;HgBr_2,\;HgI_2$의 Ion-Pair 形成恒數를, Hg電極/$HgX_2$ 또는 $HgX_2$+NaX//亞鉛아마르감 參照電極과 같은 Cell의 構成으로서 電位差法에 依하여 測定하였다.