• Bulletin of the Korean Chemical Society
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• v.35 no.6
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• pp.1789-1793
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• 2014

Pseudo-first-order rate constants ($k_{obsd}$) have been measured spectrophotometrically for the reactions of 5-nitro-8-quinolyl nicotinate (4) and 5-nitro-8-quinolyl isonicotinate (5) with alkali metal ethoxides (EtOM; M = K, Na and Li) in anhydrous ethanol at $25.0{\pm}0.1^{\circ}C$. The plots of $k_{obsd}$ vs. [EtOM] curve slightly upward for the reactions with EtOK and EtONa but are linear for the reactions with EtOLi and for those with EtOK in the presence of 18-crown-6-ether. Dissection of $k_{obsd}$ into $k_{EtO^-}$ and $k_{EtOM}$ (i.e., the second-order rate constants for the reactions with the dissociated $EtO^-$ and ion-paired EtOM, respectively) has revealed that the reactivity increases in the order $EtO^-{\approx}EtOLi$ < EtOK < EtONa for the reactions of 4 and EtOLi < $EtO^-$ < EtOK < EtONa for the reactions of 5. Comparison of the kinetic results for the reactions of 4 and 5 with those reported previously for the corresponding reactions of 5-nitro-8-quinolyl benzoate (2) and picolinate (3) has revealed that the esters possessing a pyridine ring (i.e., 3-5) are significantly more reactive than the benzoate ester 2 due to the presence of the electronegative N atom (e.g., 2 << 3 < 4 < 5). It has been concluded that $M^+$ ion catalyzes the reactions of 3-5 by increasing the electrophilicity of the reaction center through a five-membered cyclic transition state (TS) for the reaction of 3 and via a four-membered cyclic TS for the reactions of 4 and 5.

• Bulletin of the Korean Chemical Society
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• v.31 no.10
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• pp.2929-2933
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• 2010

Pseudo-first-order rate constants ($k_{obsd}$) have been measured for nucleophilic substitution reactions of 2-pyridyl benzoate 5 with alkali metal ethoxides (EtOM, M = Li, Na, K) in anhydrous ethanol. The plots of $k_{obsd}$ vs. $[EtOM]_o$ are curved upwardly but linear in the excess presence of 18-crown-6-ether (18C6) with significant decreased $k_{obsd}$ values in the reaction with EtOK. The $k_{obsd}$ value for the reaction of 5 with a given EtONa concentration decreases steeply upon addition of 15-crown-5-ether (15C5) to the reaction medium up to ca. [15C5]/$[EtONa]_o$ = 1, and remains nearly constant thereafter, indicating that $M^+$ ions catalyze the reaction in the absence of the complexing agents. Dissection $k_{obsd}$ into $k_{EtO^-}$- and $k_{EtOM}$, i.e., the second-order rate constants for the reaction with the dissociated $EtO^-$ and the ion-paired EtOM, respectively has revealed that ion-paired EtOM is 3.2 - 4.6 times more reactive than dissociated $EtO^-$. It has been concluded that $M^+$ ions increase the electrophilicity of the reaction center through a 6-membered cyclic transition state. This idea has been examined from the corresponding reactions of 4-pyridyl benzoate 6, which cannot form such a 6-membered cyclic transition state.

• Journal of the Korean Electrochemical Society
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• v.7 no.1
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• pp.16-20
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• 2004

To electropolymerize Polypyrrole(ppy) film modified with fullerene $ions(full^-)$ the cell, Au/5 mM pyrrole, 1mM fullerene, 0.1M $TBABF_4,\;CH_2Cl_2/Pt$, was employed to Prepare the wafer-like type of $electrode/ppy(full^-)ppy(full^-){\ldots}$ electrodes. They were applied to deposit alkali metal ions with the cell of Au(quartz crystal analyzer; QCA)/ppy$(full^-)$, 0.01M metal ion(aq.)/Pt. The depositing rate constant of each ion for $Li^+,\;Na^+,\;K^+,\;Rb^+\;and\;Cs^+$, determined from the first order equation was $1.60\times10^{-8},\;3.13\times10^{-11},\;1.38\times10^{-9},\;2.71\times10^{-11}\;and\;2.98\times10^{-12}mo1.s^{-1}$ respectively. The calculated stoichiometry of the ions determined by quartz crystal microbalance(QCM) at the electrodes was $Li_7C_{60},\;Na_4C_{60},\;K_3C_{60},\;Rb_1C_{60}\;and\;Cs_1C_{60}$ respectively.

• Bulletin of the Korean Chemical Society
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• v.25 no.2
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• pp.177-181
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• 2004

A PVC membrane electrode for silver ion based on a new cone shaped calix[4]arene (CASCA) as membrane carrier was prepared. The electrode exhibits a Nernstian response for $Ag^+$ over a wide concentration range ($1.0{\times}10^{-1}-8.0{\times}10^{-6}$M) with a slope of 58.2 {\pm}$ 0.5 mV per decade. The limit of detection of the sensor is $5.0{\times}10^{-6}$M. The sensor has a very fast response time (~5 s) in the concentration range of ${\leq}=1.0{\times}10^{-3}$ M, and a useful working pH range of 4.0-9.5. The proposed sensor displays excellent discriminating ability toward $Ag^+$ ion with respect to common alkali, alkaline earth, transition and heavy metal ions. It was used as an indicator electrode in potentiometric titration of $Ag^+$ with EDTA and in direct determination of silver ion in wastewater of silver electroplating.

• Journal of the Korean Electrochemical Society
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• v.9 no.3
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• pp.132-134
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• 2006

The main component governing selectivity in ion-selective electrodes and optodes is the ionophore. For this reason, a member of natural products that possess selective ion-binding properties have long been sought after. By applying this principle, the performance of tetracycline used as neutral carriers for cation selective polymeric membrane electrode was investigated. The cation ion-selective electrode based on tetracycline gave a good Nernstian response of 26.6 mV per decade for calcium ion in the activity range $1x10^{-6}M$ to $1x10^{-2}M$ with and without lipophilic additives. The optimized cation ion-selective membrane electrodes displayed very comparable potentiometric responses to various mono and di-valent cations of alkali and alkaline earth metal ions except $Mg^{2+}$.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.65-69
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• 2002

An Al film deposited on the Kovar alloy substrate was anodically-bonded to the borosilicate glass, and the bond interfaces was closely investigated by transmission electron microscopy. Al oxide was found to form a layer ~l0 nm thick at the bond interface, and fibrous structure of the same oxide was found to grow epitaxially in the glass from the oxide layer. The fibrous structure grew with the bonding time. The mechanism of the formation of this fibrous structure is proposed on the basis of the migration of Al ions under the electric field. Penetration of Al into glass beyond the interfacial Al oxide was not detected. The comparison of the amount of excess oxygen ions generated in the alkali depletion layer with that incorporated in the Al oxide suggests that the growth of the alkali-ion depletion layer is controlled by the consumption of excess oxygen to form the interfacial Al oxide.

• Proceedings of the Korean Society for Applied Microbiology Conference
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• 1979.04a
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• pp.114.2-115
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• 1979

Horikoshi등이 호 alkali 성 미생물에 관한 연구에서 분리한 수종의 cellulolytic bacteria중에서 가장 강력한 균체의 효소를 생산하는 Aeromonas 속 세균의 cellulolytic 효소에 관한 연구 결과를 보고한다. 공업적으로 생산된 효소를 사용하여 효소작용의 최적조건을 측정하고 gel filtration, ion-exchange chromatography 및 affinity chromatography 로 cel-luplytic 효소를 분리정제하였다. 본 효소의 활성 최적 pH는 7.0~8.5로 alkaline 효소였으며 반응온도 5$0^{\circ}C$에서 가장 강한 활성을 보였다. 분리 정제과정에서 carboxymethyl cellulose (CMC)에 대하여 활성이 있는 단백질이 최소 8종이상 분리되었으며 이중 1개 효소는 CMC에 대해서는 극히 낮은 활성을 보였으나 결정성 기질인 Avicel 에는 강한 활성을 보였다. 본 연구의 결과를 Cellulomonas속 세균 및 Trichoderma속 곰팡이의 효소와 그 성질을 비교 검토하였다.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.7 no.2
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• pp.141-146
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• 2021

With increasing interest in fluorinated compounds, nucleophilic fluorination reaction has been generally used for synthesizing fluorine-containing chemicals. However, alkali metal fluorides (MFs) generally have low solubility and reactivity in organic solvent. To overcome these problems, various phase transfer catalysts (PTCs) have been investigated. Calix-arene is known as to capture the metal cation(M⁺), and therefore in this review, we would like to introduce several kinds of calix-arene based PTCs, such as bis-tert-alcohol-functionalized crown-6-calix[4]arene (BACCA), oligo-ethylene glycol linked bis-triethyleneglycol crown-5-calix[4]arene (BTC5A), and ionic liquid functionalized calix-arene based catalyst, as well as ion-pair receptor crown-6-calix[4]arene-capped calix[4]pyrrole.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.149-149
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• 2000

Alkali and alkali-earth metal on si(001) surface has been investigated widly for both scientific and technological aspects. In particular, the Ba/Si(001) system has been studied by several groups and they reported many phases such as (2$\times$3), (2$\times$4) and c(6$\times$2) 표 LEED and AES for various temperature and coverages. But there has not been the result of the atomic structure for these phases. Recently some works about the atomic structure of Ba/Si(001) at only room temperature were presented. In this study, we investigated 3-dimensional atomic structure and growth mode of Ba layer on si(001) by coaxial impact collision ion scattering spectroscopy (CAISS) at room temperature and high temperature.

• Journal of Environmental Science International
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• v.5 no.2
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• pp.211-220
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• 1996

New thin-and diselena-crown ethers containing two suffer and selenium donor atoms have been prepared. And then, mercury ($Hg^{2+}$) ion-selective electrodes with PVC-plasticizer (STPB) based on some macrocycles as neutral carriers were also made. The electrochemical selectivities for various ions, and the effects for macrocycles, matrix of membranes, ratio of plasticizer to macrowcles, concentration and pH of test solution were investigated on the $Hg^{2+}$ ion-selective electrodes. The 1, 10-diselena-18-crown-6-PVC-STPB (sodium tetraphenylborate) exhibited good linear responses of ${28.2}\pm{0.6}$ decade-1 for $Hg^{2+}$ ion in the conientration ranges of $10^{-2}~10^{-6}$ M $Hg^{2+}$ ion. This electrode exhibited comparatively good selectivities for $Hg^{2+}$ ion in comparison with alkali and alkaline earth metal ions, some heavy metal ions and rare earth metal ion in the range of pH 2.5~6.0. In addition, this electrode was applied as a sensor in the titration of $Hg^{2+}$ ion with $1^-$ ion in water.