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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Bulletin of the Korean Chemical Society
Journal Basic Information
Journal DOI :
Korean Chemical Society
Editor in Chief :
Byeong Moon Kim
Volume & Issues
Volume 18, Issue 12 - Dec 1997
Volume 18, Issue 11 - Nov 1997
Volume 18, Issue 10 - Oct 1997
Volume 18, Issue 9 - Sep 1997
Volume 18, Issue 8 - Aug 1997
Volume 18, Issue 7 - Jul 1997
Volume 18, Issue 6 - Jun 1997
Volume 18, Issue 5 - May 1997
Volume 18, Issue 4 - Apr 1997
Volume 18, Issue 3 - Mar 1997
Volume 18, Issue 2 - Feb 1997
Volume 18, Issue 1 - Jan 1997
Selecting the target year
The Effect of Acyl Substituent on the α-Effect in the Aminolysis of p-Nitrophenyl X-Substituted Benzoates
엄익환 ; 정은경 ; 권혜진 ; 권동숙 ;
Bulletin of the Korean Chemical Society, volume 18, issue 9, 1997, Pages 911~913
Raman Spectroscopic Study on the Acid Behavior of Aqua-Cations in Non-Aqueous Solution
한근옥 ; 김은수 ; 이상희 ; 유수창 ; 이국행 ;
Bulletin of the Korean Chemical Society, volume 18, issue 9, 1997, Pages 914~915
Spectroscopic Studies on the High-
Prepared by Electrochemical Oxidation
박정철 ; Alain Wattiaux ; Jean-Claude Grenier ; 김동훈 ; 최진호 ;
Bulletin of the Korean Chemical Society, volume 18, issue 9, 1997, Pages 916~922
A superconducting phase La2CuO4+δ (Tc=44 K) has been prepared by electrochemical oxidation which allows the oxygen to intercalat into the La2O2 layers. According to the Cu K-edge X-ray absorption near edge structure spectroscopic analysis, the oxidized phase shows an overall spectra shift of about 0.5 eV to a higher energy region compared to the as sintered one with the occurrence of an additional peak corresponding to the transition to the |1s13dn+1L-14pσ1 > final state, indicating the oxidation of CuO2 layer. From the X-ray photoelectron spectroscopic studies, it is found that the binding energy of La 3d5/2 is significantly shifted from 834.3 eV (as sintered La2CuO4) to 833.6 eV (as electrochemically oxidized La2CuO4+δ), implying that the covalency of the (La-O) bond is decreased due to the oxygen intercalation. The O 1s spectra do not provide an evidence of the superoxide or peroxide, but the oxide (O2-) with the contaminated carbonate (CO32-) based on the peaks at 529 eV and 532 eV, respectively, which is clearly confirmed by the Auger spectroscopic analysis. Oxygen contents determined by iodometric titration (δ=0.07) and thermogravimetry (δ=0.09) show good coincidence each other, also giving an evidence for the "O2-" nature of excess oxygen. From the above results, it is concluded that "O2-" appeared as O 1s peak at 528.6 eV is responsible for superconductivity of La2CuO4+δ.
Conformational Transition of Form II to Form Ⅰ PoLy(L-proline) and the Aggregation of Form Ⅰ in the Transition: Water-Propanol Solvent System
Bulletin of the Korean Chemical Society, volume 18, issue 9, 1997, Pages 922~928
The conformational transition of poly(L-proline) (PLP), Form Ⅱ → Form Ⅰ and the intermolecular aggregation of the product, Form Ⅰ, during and after the transition in water-propanol (1:7, 1:9, 1:15.7, and 1:29 v/v) were studied. For the study, the viscosity change and excess light scattering intensity were measured in the course of the transition which was determined by the Form Ⅰ fraction, fI of the sample solution. For the PLP sample of molecular weight Mv=31,000 the experimental results show that the reaction course is roughly divided into three regions: in the first region [fI=0.27 to 0.40 (- [α]D=400 to 330)], the conformational change of Form Ⅱ → Form Ⅰ occurs with decrease of viscosity, in the second region [fI=0.40 to 0.80 (- [α]D=330 to 120)], a partial side-by-side (p-S-S) type aggregation in which Form Ⅰ blocks interact with each other, which induces the increase of viscosity, starts to occur, and in the third region [fI=0.80 to 1.00 (- [α]D=120 to 15)], a side-by-side type (raft like) aggregation of Form Ⅰ or an end-to-end (E-E) type aggregation occurs according to the solvent situation, i.e., in a water-rich medium [water-propanol (1:9 or 1:7 v/v)], the (S-S) type aggregation with a gross decrease in viscosity occurs while in a water-poor medium [water-propanol (1:29 or 1:15.7 v/v), the (E-E) type aggregation with a large increase in viscosity occurs. The (S-S) type aggregation was promoted at high temperatures. Based on the structure of PLP, a reasonable mechanism for the (p-S-S) and (S-S) aggregation which occurs with the transition of Form Ⅱ → Form Ⅰ is considered. The suggested mechanism was also supported by the result of chain length effect of PLP for the aggregation.
The Formation of Rope- and Pebbles-Type Aggregation from the Micro-End-to-End and -Side-by-Side Aggregates in Poly(L-proline) Solutions
Bulletin of the Korean Chemical Society, volume 18, issue 9, 1997, Pages 929~933
Morphological studies in the micro-end-to-end (m-E-E) and micro-side-by-side (m-S-S) aggregations were conducted by using of scanning electron microscope (SEM) for the samples precipitated by heating of the end-products of the transition of FormⅡ (left-handed helix, three peptides per turn, 31) Form Ⅰ (right-handed helix, 3.3 peptides per turn, 103) in poly(L-proline) (PLP) in acetic acid(water)-propanol (1:9 v/v) solvent. The observed morphology for the solide state shows a rope (or super helical) type and pebbles type aggregate for the (m-E-E) and (m-S-S) aggregate respectively. The viscosities were also measured during the heat-precipitation in order to elucidate the process of formation of the rope- and pebbles-type aggregates. The result for the (m-E-E) aggregations exhibit two steps, i.e., at first, the viscosity increases with time (step 1), thereafter it decrease until attain the last value (step 2). But the (m-S-S) aggregations show only one step in the decreases in viscosity. On the bases of all experimental results it is possible to propose a reasonable mechanism for the formation of the two types of aggregates of the (m-E-E) and (m-S-S).
Interaction of Mastoparan B and Its Ala-Substituted Analogs with Phospholipid Bilayers
박남규 ; 서정길 ; 구희정 ; 김승호 ; Sannamu Lee ; Gohsuke Sugihara ; 김광호 ; 박장수 ; 강신원 ;
Bulletin of the Korean Chemical Society, volume 18, issue 9, 1997, Pages 933~938
The interaction of mastoparan B, a tetradecapeptide toxin found in the hornet Vespa basalis, with phospholipid bilayers was investigated. Synthetic mastoparan B and its analogs, obtained by substituting one hydrophilic amino acid (2-Lys, 4-Lys, 5-Ser, 8-Ser, 11-Lys, or 12-Lys) in mastoparan B with Ala, were studied. Mastoparan B and its analogs were synthesized by the solid-phase method. As shown by circular dichroism spectra, mastoparan B and its analogs adopted an unordered structure in buffer solution. All peptides took an α-helical structure, and the α-helical content of its analogs increased in the presence of neutral and acidic liposomes as compared to that of mastoparan B. In the calcein leakage experiment, we observed that mastoparan B interacted more weakly with lipid bilayers in neutral and acidic media than its analogs. Mastoparan B also showed slightly lower antimicrobial activity and hemolytic activity towards human erythrocytes than its analogs. These results indicate that the greater hydrophobicity of the amphiphilic α-helix of mastoparan B by replacement with alamine residues results in the increased biological activity and helical content.
A Series of Quinoline-2-carboxylic Acid Derivatives: New Potent Glycine Site NMDA Receptor Antagonists
김란희 ; 최진일 ; 최승원 ; 이광숙 ; 정영식 ; 박우규 ; 성철민 ; 박노상 ;
Bulletin of the Korean Chemical Society, volume 18, issue 9, 1997, Pages 939~945
Several types of 4-substituted-quinoline-2-carboxylic acid derivatives possessing different substituents at C4-position such as sulfonyl, phosphonyl, carbonyl groups, or a flexible alkyl chain have been synthesized and evaluated for their in vitro antagonistic activity at the glycine site on the N-methyl-D-aspartate (NMDA) receptor. Of them, 5,7-dichloro-4-(tolylsulfonylamino)-quinoline-2-carboxylic acid 9 was found to have the best in vitro binding affinity with IC50 of 0.57 μM. On the other hand, in compounds 21 and 22 the introduction of flexible alkyl chains on C4 of the quinoline mother nuclei caused a significant decrease of the in vitro binding affinity. In addition, replacement of polar carboxylic acid group on C2 by neutral bioisosteres in compounds 23a-d also seems to be disadvantageous to in vitro activity. In the structure-activity relationship (SAR) study of the 4-substituted quinoline-2-carboxylic acid acid derivatives, it was realized that the substitution pattern on C4 significantly influences on the binding affinity for the glycine site of NMDA receptor and the binding affinity might be increased by the introduction of a suitable electron rich substituent at C4 which has the ability of H-bonding donor.
Structure and Reactivity in the Reaction of Diazoindanes and Diazoindanones with Triphenylphosphine : The Formation of Mono-, and Bisphosphazines and Hydrazone-Compounds
성대동 ; 강동효 ; 류준하 ;
Bulletin of the Korean Chemical Society, volume 18, issue 9, 1997, Pages 945~952
The reactions of diazoindanes and diazoindanones with triphenylphosphine have been studied in acetonitrile. The diazoindanes and diazoindanones react with triphenylphosphazine. The reaction of 1,3-bis(diazo)indan-2-one with a tenfold excess of triphenylphosphine in dry acetonitrile gave the 1,3-bis(phosphazino)indan-2-one, however in acetonitrile containing below of 1% water, the 1,3-bis(hydrazono)indan-2-one was produced by hydrolysis. The phosphazine compound could be easily converted into bishydrazone by recrystallization, due to small amounts of water in the solvent. The reactivity of triphenylphosphine toward diazoindanes and diazoindanones depends on the structrue of the diazo compounds.
Copper Oxide-Modified Polymeric Composite Elecrodes for Amperometric Detection of Carbohydrates in LCEC Analysis
정혜경 ; 박종만 ;
Bulletin of the Korean Chemical Society, volume 18, issue 9, 1997, Pages 952~957
Modified polymeric composite electrodes having highly dispersed CuO particles through the electrode matrix were prepared for LCEC or flow injection analysis of carbohydrates. The composite electrodes were prepared by incorporating carbon black and highly dispersed copper oxide particles in polystyrene matrix cross-linked with divinylbenzene. The analytical characteristics of the electrodes for LCEC and flow injection analysis of carbohydrates were evaluated. Improved performance in LCEC and flow injection analysis of carbohydrates is demonstrated in terms of sensitivity, reproducibility, stability and surface renewability. It was possible to get improved performance of the electrodes as well as adaptability of the electrodes for practical applications by employing highly dispersed catalyst particles through the electrode matrix and robust polymeric electrode matrix.
Surface Structure of Blend Films of Styrene/Acrylonitrile Copolymer and Poly(methyl methacrylate)(PMMA) or Hydrolyzed PMMA
이원기 ; K. Tanaka ; A. Takahara ; T. Kajiyama ; 하창식 ;
Bulletin of the Korean Chemical Society, volume 18, issue 9, 1997, Pages 958~961
The compatibility and the surface structure of blends of poly(styrene-co-acrylonitrile) (SAN) with either poly(methyl methacrylate) (PMMA) or hydrolyzed PMMA (H-PMMA) were studied in terms of film thickness, interaction, and surface free energy difference on the basis of X-ray photoelectron spectroscopy (XPS), attenuated total reflection Fourier transform IR spectroscopy and atomic force microscopy. The XPS measurement showed that the surface enrichment of (PMMA/SAN) blends with different AN contents of SAN and with different carboxyl acid contents of PMMA was dependent on the molecular interaction, the surface free energy difference between components and the sample preparation history. It was found that the compatibility of H-PMMA and SAN was reduced with increasing carboxyl acid content of PMMA.
Rates of Conformational Change of 3,3-Dimethylpiperidine and Solvent Effects on Its Conformation When Coordinated to the Paramagnetic Undecatungstocobalto(II)silicate Anion Studied by 1H NMR Spectroscopy
현재원 ; 소현수 ;
Bulletin of the Korean Chemical Society, volume 18, issue 9, 1997, Pages 961~965
1H NMR spectra of 3,3-dimethylpiperidine (1) at -70 to 30 ℃ exhibit gradual change from slow to rapid exchange between two alternate chair forms. The exchange rate constant was determined as a function of temperature by simulating the line shape of the signal from the two methyl groups using the modified Bloch equations. The resulting free energy of activation is ΔG* = 44.4±1.9 kJ mol-1 at 298 K. The 1H NMR spectrum of a D2O or dimethylsulfoxide-d6 (DMSO-d6) solution containing 1 and [SiW11CoⅡO39]6- exhibits separate signals for the free ligand and the complex, indicating that the ligand exchange is slow on the NMR time scale. In D2O the piperidine ring is frozen as a chair form even at room temperature with the cobalt ion bonded to the axial position of the nitrogen atom. When DMSO-d6 is added to the D2O solution, the NMR spectral change suggests that a rapid exchange occurs between the chair form and another conformer. It is proposed that the conformation of ^b1^b coordinated to [SiW11CoⅡO39]6- in DMSO-d6 is close to a twist form.
Approximate Nonrandom Two-Fluid Lattice-Hole Theory. General Derivation and Description of Pure Fluids
유기풍 ; 신훈용 ; 이철수 ;
Bulletin of the Korean Chemical Society, volume 18, issue 9, 1997, Pages 965~972
An approximate molecular theory of classical fluids based on the nonrandom lattice statistical-mechanical theory is presented. To obtain configurational Helmholtz free energy and equation of state (EOS), the lattice-hole theory of the Guggenheim combinatorics is approximated by introducing the nonrandom two-fluid theory. The approximate nature in the derivation makes the model possible to unify the classical lattice-hole theory and to describe correctly the configurational properties of real fluids including macromolecules. The theory requires only two molecular parameters for a pure fluid. Results obtained to date have demonstrated that the model correlates quantitatively the first- and second-order thermodynamic properties of real fluids. The basic simplicity of the model can readily be generalized to multicomponent systems. The model is especially relevant to (multi) phase equilibria of systems containing molecularly complex species.
Oxygen Evolution Reaction at Electrodes of Single Phase Ruthenium Oxides with Perovskite and Pyrochlore Structures
최은옥 ; 권영욱 ; 모선일 ;
Bulletin of the Korean Chemical Society, volume 18, issue 9, 1997, Pages 972~976
Single phase ruthenium oxides with perovskite (ATi1-xRuxO3 (A=Ca, Sr)) and pyrochlore structure (Bi2Ru2O7, Pb2Ru2O6.5) have been prepared reproducibly by solid state reaction methods and their electrocatalytic activities for oxygen evolution have been examined by Tafel plots. Tafel slopes vary from a low value of 42 mV/decade up to 222 mV/decade at room temperature. The high exchange current densities and high Tafel slopes compared with those obtained from the RuO2 DSA electrode at the crystalline single phase metal oxide electrodes suggest that they are better electrocatalysts at low overpotentials. A favorable change in the Tafel slope for the oxygen evolution reaction occurs as the ruthenium content increases. Substitution of Ti for Ru in the perovskite solid solutions enhanced their chemical stability by losing marginal electrochemical activity.
Ligand Field Approach to
Magnetism Based on Intermediate Field Coupling Scheme
최진호 ; 김종영 ;
Bulletin of the Korean Chemical Society, volume 18, issue 9, 1997, Pages 976~981
The magnetic susceptibilities of molybdenum ions with 4d1 electronic configuration in the octahedral crystal field were calculated on the basis of ligand field theory. The experimental magnetic susceptibilities for molybdenum ions, which are stabilized at the octahedral site in the perovskite lattice of Ba2ScMoⅤO6 and Sr2YMoⅤO6, were compared with the theoretical ones. We have tried to fit their temperature dependence of magnetic susceptibility with ligand field parameters, spin-orbit coupling constant ζSO, and orbital reduction parameter κ according to intermediate field coupling and strong field theory. Strong field coupling theory could not explain experimental curves without unrealistically large axial ligand field, since it ignores the mixing up between different state via spin-orbit interaction and ligand field. On the other hand, the intermediate field coupling theory could successfully reproduce experimental data in octahedral and trigonal ligand field. The fitting result demonstrates not only the fact that spin-orbit interaction is primarily responsible for the variation of magnetic behavior but also the fact that effective orbital overlap, enhanced by cubic crystal structure, reduces significantly orbital angular momentum as indicated by κ parameter.
Ab initio Nuclear Shielding Calculations for Some X-Substituted Silatranes Using Gauge-Including Atomic Orbitals
김동희 ; 이미정 ;
Bulletin of the Korean Chemical Society, volume 18, issue 9, 1997, Pages 981~985
13C, 15N, and 29Si NMR chemical shifts have been computed for selected X-substituted silatranes (X=Cl, F, H, CH3) using Gauge-Including Atomic Orbitals (GIAO) at the Hartree-Fock level of theory. The isotropic 13C chemical shifts are largely insensitive to substituent-induced structural changes. In this study, the isotropic 13C chemical shifts between 1-methyl- and 1-hydrogensilatranes by GIAO-SCF calculation at the HF/6-31G level are very similar. But the results of 1-chloro- and 1-fluorosilatranes are about 4 ppm different from the experimental values. In contrast, the isotropic 15N and 29Si chemical shifts and the chemical shielding tensors are quite sensitive to substituent-induced structural changes. These trends are consistent with those of the experiment. The isotropic 15N chemical shift demonstrates a very clear correlation with Si-N distance. But in case of 29Si the correlations are not as clean as for the 15N chemical shift; the calculated variation in the 29Si chemical shift is much larger.
Reaction of Gae-Phase Atomic Hydrogen with Chemisorbed Hydrogen Atoms on an Iron Surface
Kim, M. S. ; Ree, J. ;
Bulletin of the Korean Chemical Society, volume 18, issue 9, 1997, Pages 985~994
The reaction of gas-phase atomic hydrogen with hydrogen atoms chemisorbed on Fe(110) surface is studied by use of classical trajectory procedures. Flow of energy between the reaction zone and bulk solid phase has been treated in the generalized Langevin equation approach. A London-Eyring-Polanyi-Sato energy surface is used for the reaction zone interaction. Most reactive events are found to occur in strong single-impact collisions on a subpicosecond scale via the Eley-Rideal mechanism. The extent of reaction is large and a major fraction of the available energy goes into the vibrational excitation of H2, exhibiting a vibrational population inversion. Dissipation of reaction energy to the heat bath can be adequately described using a seven-atom chain with the chain end bound to the rest of solid. The extent of reaction is not sensitive to the variation of surface temperature in the range of Ts=0-300 K in the fixed gas temperature, but it shows a minimum near 1000 K over the Tg=300-2500 K.
Reactions of Phosphites with Nitroalkene Derivatives: Syntheses of
-Keto Phosphonates and
김대영 ; 오동영 ;
Bulletin of the Korean Chemical Society, volume 18, issue 9, 1997, Pages 994~998
The addition of phosphite derivatives 1 to nitroalkenes 2 afforded α-phosphoryl nitronates which, on treatment MCPBA, were converted β-keto phosphonates 3. A versatile reaction conditions to generate α-phosphoryl nitronates were examined. α-Cyanoalkylphosphonates 6 were prepared from the diethyl trimethylsilyl phosphite (DTSP) 1c with nitroalkenes 2 and followed by reduction.
[4+4] Cyclodimer of tert-Butyl 9-Anthroate and Furan and [4+4] Cyclodimers of Alkyl 9-Anthroate
노태희 ; 임희준 ; 김대균 ; 전경문 ;
Bulletin of the Korean Chemical Society, volume 18, issue 9, 1997, Pages 998~1002
Irradiation of tert-butyl 9-anthroate and furan through a Uranium glass filter gave the [4+4] cyclodimer (21.8%) of tert-butyl 9-anthroate and furan and the 1,4-10',9' cyclodimer (4.2%) of tert-butyl 9-anthroate as well as the 9,10-10',9' cyclodimer (65.7%) of tert-butyl 9-anthroate. The [4+4] cyclodimer of tert-butyl 9-anthroate and furan was found to be thermally dissociated into their unit components with the activation enthalpy of 35.6 kcal/mole and the activation entropy of 7.6 eu, and photochemically dissociated to produce excited tert-butyl 9-anthroate. Quantum yields for the photodissociation to tert-butyl 9-anthroate and the formation of excited tert-butyl 9-anthroate in cyclohexane at room temperature were determined to be 0.56 and 0.19, respectively. The 1,4-10',9' cyclodimer of tert-butyl 9-anthroate in DMF was thermally dissociated into tert-butyl 9-anthroate with the activation enthalpy of 34.8 kcal/mole and the activation entropy of 16.4 eu. Upon irradiation, the [4+4] cyclodimers of tert-butyl 9-anthroate and the [4+4] cyclodimers of methyl 9-anthroate were quantitatively dissociated. However, no adiabatic photoreversion was observed from any of the cyclodimers. Quantum yields for the photodissociation in cyclohexane at room temperature were measured and compared.
1H NMR Study of Aziridine Derivatives Coordinated to the Paramagnetic Undecatungstocobalto(II)silicate and -nickelo(II)silicate Anions
박석민 ; 서현수 ;
Bulletin of the Korean Chemical Society, volume 18, issue 9, 1997, Pages 1002~1006
1H NMR spectra of D2O solutions containing 2,2-dimethylaziridine (1) or 2-methylaziridine (2) and [SiW11COⅡO39]6- (SiW11Co) or [SiW11NiⅡO39]6- (SiW11Ni) exhibit separate signals for the free ligand and the complex, indicating that the ligand exchange is slow on the NMR time scale. Identified are two linkage isomers with the methyl group of 2 at trans or cis position with respect to the metal. The isotropic shifts of 1 and 2 coordinated to SiW11Ni originate mainly from the contact shifts, and they agree reasonably with the relative values reported for similar ligands coordinated to bis(2,4-pentanedionato)nickel(Ⅱ). The isotropic shifts for the SiW11Co complexes were separated into contact and pseudocontact contributions. The pseudocontact shifts show that (χ∥-χ⊥) is positive, while that for the SiW11Co complexes of pyridine derivatives is negative. This result indicates that the ordering of dxy and dxz, dyz orbitals in SiW11Co complexes can be reversed by ligands.
Analysis of Complex Forced Raleigh Scattering Decay Profiles for the Diffusion of Methyl Yellow in Binary Solution
박하선 ; 성정문 ; 이현정 ; 장태현 ; Daniel R. Spiegal ;
Bulletin of the Korean Chemical Society, volume 18, issue 9, 1997, Pages 1006~1010
The nature and analysis methods of complicated decay profiles found in forced Rayleigh scattering (FRS) have been investigated for the probe diffusion of methyl yellow in 2-propanol. The complementary shifted and ground state grating effect, which is known to be the origin of non-single exponential decays, was analyzed by non-linear regression fitting to a double exponential model function. We confirmed that the parameters were highly correlated so that it was difficult to extract a unique set of parameters in the presence of experimental noise. Nevertheless, a reasonable range of decay time constants could be estimated from the grating spacing dependence.
Structure-Reactivity Relationship of Substituted Phenylethyl Arenesulfonates with Substituted Pyridines under High Pressure
박헌영 ; 손기주 ; 정덕영 ; 여수동 ;
Bulletin of the Korean Chemical Society, volume 18, issue 9, 1997, Pages 1010~1013
Nucleophilic substitution reactions of (Z)-phenylethyl (X)-benzenesulfonates with (Y)-pyridines were investigated in acetonitrile at 60 ℃ under respective pressures. The magnitudes of the Hammett reaction constants, ρX, ρY and ρZ indicate that a stronger nucleophile leads to a greater degree of bond formation of C-N and a better leaving group is accompanied by a less degree of bond breaking. The magnitude of correlation interaction term, ρij can be used to determine the structure of the transition state (TS) for the SN reaction. As the pressure is increased, the Hammett reaction constants, ρX and |ρY|, are decreased, but correlation interaction coefficient, ρXZ and |ρYZ|, are increased. The results indicate that the reaction of (Z)-phenylethyl (X)-benzenesulfonates with (Y)-pyridines probably moves from a dissociative SN2 to early-type concerted SN2 mechanism by increasing pressure. This result shows that the correlation interaction term ρij can be useful tool to determine the structure of TS, and also the sign of the product ρXZ·ρYZ can be predict the movement of the TS.
Complexation and Conformational Flexibility of Calixarence Dibenzocrown Ethers
김종승 ; Akira Ohki ; 조문환 ; 김종국 ; 라도영 ; 조남숙 ; Richard A. Bartsch ; 이근우 ; 오원진 ;
Bulletin of the Korean Chemical Society, volume 18, issue 9, 1997, Pages 1014~1017
1,3-Dipropyloxycalixarene dibenzocrown ethers were synthesized in the fixed 1,3-alternate conformation by the reaction of 1,3-dipropyloxycalixarenes with a dibenzo dimesylates. Complexation toward alkali metal ions using ISEs showed a high cesium selectivity. Conformational flexibility of the corresponding 1,3-alternate calixcrown ether (4) with respect to the NMR time scale is found to depend on the temperature and polarity of the NMR solvent.
Stoichiometric Solvation Effects. Part 4. Product-Rat Correlations for Solvolyses of p-Methoxyphenyl Chloroformate in Alcohol-Water Mixtures
구인선 ; 양기열 ; 구자찰 ; 박종근 ; 이익준 ;
Bulletin of the Korean Chemical Society, volume 18, issue 9, 1997, Pages 1017~1021
Solvolyses of p-methoxyphenyl chloroformate in water, D2O, CH3OD, 50% D2O-CH3OD, and in aqueous binary mixtures of acetone, ethanol and methanol are investigated at 25.0 ℃. Product selectivities are reported at 25 ℃ for a wide range of ethanol-water and methanol-water solvent compositions. The Grunwald-Winstein plots of first-order rate constants for p-methoxyphenyl chloroformate with YCl (based on 1-adamantyl chloride) show marked dispersions into three separate curves for the three aqueous mixtures with a small m value and a rate maximum for aqueous alcohol solvents. Third-order rate constants, kww, kaw, kwa and kaa were calculated from the observed kww and kaa values together with kaw and kwa calculated from the intercept and slope of the plot of 1/S vs. [alcohol]/[water]. The calculated rate constants, kcalc and mol % of ester agree satisfactorily with those of the observed rate constants, kobs and mol % of ester, supporting the stoichiometric solvation effect analysis. The kinetic solvent isotope effects determined in water and methanol are consistent with the proposed mechanism of the general base catalyzed carbonyl addition-elimination.
Synthesis and Characterization of Bis(5,6-dihydro-1,4-dithiin-2,3-dithiolato)nickel(II), nickel(III) and of Related Dialkyl Nickel(III) Dithiolene Complexes
김영진 ; 최성낙 ; 오영희 ;
Bulletin of the Korean Chemical Society, volume 18, issue 9, 1997, Pages 1022~1028
The reaction between Ni(Ⅱ) and sodium salt of 5,6-dihydro-1,4-dithiin-2,3-dithiolate (DDDT2-) in the presence of oxygen results in the formation of Ni(Ⅲ) species, Ni(DDDT)2-, which is isolated as tetraalkylammonium salt. The same reaction performed in the absence of oxygen yields dianionic Ni(Ⅱ) species, Ni(DDDT)22-, which is also isolated as the tetraethylammonium salt. The bis(5,6-dihydro-1,4-dithiin-2,3-dithiolato) nickelate (Ⅱ) dianion, Ni(DDDT)22-, reacts with methyl iodide to yield unusually stable bis(methylthio)dithiolene complex, Ni(CH3)2C8H8S8. All the isolated dithiolato-nickel(Ⅱ) and nickel(Ⅲ) complexes are characterized by 1H NMR, UV/Vis, IR and mass spectroscopic methods. The internal redox reaction of the nickel(Ⅱ)-dithiolate has been studied by spectro-electrochemical method and the results were compared with those of other metal-dithiolenes. The alkylated nickel(dithiolene) complex presumably undergoes cis-trans isomerization reaction in solution, judging from the experimental results of variable-temperature 1H NMR measurements.
Influence of Amphoteric Behaviour of Oxide Materials on the Selectivity of Micro and Mesoporous Ceramic Membranes
L. Cot ; A. Larbot ;
Bulletin of the Korean Chemical Society, volume 18, issue 9, 1997, Pages 1028~1031
Electrostatic interaction is a very important parameter for the membrane selectivity. In this work, the electrical double layer establishment on the surface of metal oxide material from the Stern-Grahame model has been described. Then, some examples of rejection using micro and mesoporous ceramic membranes have been given. A correlation between the charges of the membrane material and the species to be filtered has been precised. Two rejection mechanisms have to be taken into account the size of the solutes and the electrostatic interactions.
Synthesis of the 1
-Methylcarbapenem Key Intermediate
구양모 ; 서민효 ; 이윤영 ;
Bulletin of the Korean Chemical Society, volume 18, issue 9, 1997, Pages 1032~1034
Synthesis of p-Phenylcalixarene
노광현 ; 권경미 ; 김보형 ;
Bulletin of the Korean Chemical Society, volume 18, issue 9, 1997, Pages 1034~1036
Improved Glass-Lined Stainless Steel Packed Microcolumns of 0.3 mm I.D.
정원조 ; 이충식 ; 안현주 ;
Bulletin of the Korean Chemical Society, volume 18, issue 9, 1997, Pages 1036~1038