• Bulletin of the Korean Chemical Society
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• v.22 no.1
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• pp.59-62
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• 2001

The dried fruit-body of Daedaleopsis tricolor was extracted by the petroleum ether. The extracts were purified by liquid-liquid extraction, column chromatography, and recrystallization. The purified compound was a colorless orthorhombic crystal form. Its melting point, molecular weight and molar extinction coefficient $(\varepsilon)$ were estimated $168-170^{\circ}C$, 424 and 3,935 at 208 nm, respectively. Its structure was elucidated to be 20(29)-lupen-3-one by UV-Vis, FT-IR, NMR and X-ray crystallographic analysis. It showed antifungal activities against Saccharomyces cerevisiae and Microsporum gypseum, and antibacterial activities against Escherichia coli, Proteus vulgaris, Pseudomonas pyocyanea, Bacillus subtilis, and Staphylococcus aureus. In addition, this compound showed an antioxidative activity on lipid-peroxidation by 6.4%.

• Bulletin of the Korean Chemical Society
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• v.15 no.5
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• pp.369-374
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• 1994

Self-assembled (SA) and Langmuir-Blodgett (LB) monolayers of arachidic acid on silver surfaces have been investigated by a reflection-absorption Fourier transform infrared spectroscopy. Arachidic acid was adsorbed on silver as carboxylate with its two oxygen atoms bound symmetrically to the surface. Although both the SA and LB monolayers consisted of fully extended trans zigzag carbon chains, a closer examination indicated that the SA monotayers should possess a more ordered crystalline structure than the LB monolayers. The infrared spectral data dictated that the extent of methyl group exposure at the air-film interface was greater in the SA monolayers than the LB monolayers, in agreement with the contact angle measurement. From a theoretical analysis, the alkyl chains in each monolayers seemed to be tilted away from the surface normal by less than $3.5^{\circ}$, but in opposite directions. Arachidic acid monolayers were concluded to have same structure as stearic acid monolayers.

• Bulletin of the Korean Chemical Society
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• v.21 no.4
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• pp.434-440
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• 2000

We present the results of computer simulation for the steady shear flows of rodlike molecules using nonequi-librium molecular dynamics simulation (NEMD) method. The model particle is a rigid rod composed of lin-early connected 6-sites and the Lennard-Jones 12-6 potential governs interactions between sites in different molecules. The system of rodlike molecules exhibits the change of orientational structure, that is, isotropic-nematic transition at high shear rates. We elucidate the nature of the ordered system developed from an isotro-pic phase by steady shear through an analysis of various quantities: orientational order parameters, orientational pair correlation functions, orientational distribution function, and snapshots of configurations. The effects of temperature and density on the shear rate dependence of orientational structure are described.

• Bulletin of the Korean Chemical Society
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• v.15 no.12
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• pp.1070-1079
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• 1994

Quantitative Structure-Activity Relationship (QSAR) studies are performed for the sets of 40 quinolones and 47 naphthyridines. Net charge, van der Waals volume, polarizability, and dipole moment are empolyed as theoretical descriptors(independent variables) to find the relationship between activity and physicochemical properties such as electrostatic effect, steric effect, and transferability. The results are analyzed by the regression and the factor analysis. It is found that for Gram-negative bacteria, the QSAR of quinolone and naphthyridine are substantially different: to describe the activity, the electrostatic effect is the most important for quinolone, and the steric effect and the transferability for naphthyridine.

• Bulletin of the Korean Chemical Society
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• v.20 no.10
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• pp.1172-1176
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• 1999

Nucleophilic substitution reaction of Y-benzyl bromide with X-pyridines are investigated in DMSO at 45.0℃. Biphasic rate dependence is observed on varying the substituents in the substrate (Y) as well as in the nucleophile (X). The two well-defined straight lines in the Hammett (ρy) and Bronsted ( βx) plots are interpreted to indicate the changes in transition-state structure, a decrease in bond cleavage as the substituent on the substrate is changed from electron-donors ( ρy < 0) to electron-acceptors ( ρy > 0), and an increase in the extent of bond formation with the corresponding changes of the substituent on the pyridine. A Jencks' type analysis of separate polar (ρ) and resonance (ρr) effects can also be accounted for by the change of the transition-state structure, not by the variable combination of polar and resonance effects.

• Bulletin of the Korean Chemical Society
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• v.21 no.12
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• pp.1187-1192
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• 2000

Ternary (Mo-Ru-Pd) and binary (Mo-Ru, Mo-Pd) alloys have been prepared using an Ar arc melting furnace. Mo and the noble metals, Ru and Pd, are the constituents of metallic insoluble residues, which were found in the early days of post-irradiation studies on uranium oxide fuels. In the present study, the structure of the alloys was evaluated using a powder X-ray diffractometer. Unit cell parameters were determined by least squares refinements of powder X-ray diffraction data. Scanning electron microscopic analyses of the surface of the alloys indicated that surface morphology was dependent on the crystallographic structure as well as its composition. Measurements of the magnetic susceptibility of the alloys showed evidence of superconducting transition from 3 to 9.2 K. Among the ternary and binary alloys, the ${\sigma}-phase$ showed the highest superconducting transition temperature,~9.2 K.

• Bulletin of the Korean Chemical Society
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• v.22 no.12
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• pp.1350-1360
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• 2001

The synthesis and characterization of very stable Pd(Ⅱ) η1-imine complexes of bis(3,4-dialkyloxybenzylidene-3', 4'-dialkyloxyaniline)dichloropalladium(Ⅱ) with alkyl chain of hexyl (8), octyl (9), decyl (10) and dodecyl (11) groups, a nd of bis(4-ethyloxybenzylidene-4'-ethyloxyaniline)dichloropalladium(Ⅱ) as a model complex are described. The molecular structure with twisted board-like geometry of the complex resulting from the coordination of Pd(Ⅱ) with η1-imine bonding was confirmed by X-ray crystallographic analysis of the model complex. In contrast to the imine ligands, all the complexes with an exception of 11 display a thermally stable monotropic smectic A mesophase without any decomposition of the complex. These results, characterized by a combination of differential scanning calorimetry, optical polarized microscopy, and powder X-ray scattering experiments, are discussed.

• Bulletin of the Korean Chemical Society
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• v.16 no.7
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• pp.661-666
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• 1995

The surface structure of the adsorption site for the identification of active sites involved in the Ziegler-Natta catalyst was studied by surface science techniques. As an example of a real catalyst, TiCl3 single crystals were prepared in a gradient furnace designed for this study and characterized by Auger Electron Spectroscopy (AES) and Low Energy Electron Diffraction (LEED) under ultrahigh vacuum condition. The chlorine covered Ti (0001) surface was employed as a model catalyst for the study of Ziegler-Natta catalyst. The diffuse LEED (DLEED) technique for the surface structural determination was applied to this disordered chlorine adsorbed on Ti (0001) surface. The diffuse scattering intensities were measured by a TV-computer method using a low light level video camera. From an analysis of two catalyst systems, the informations for the surface structure of the model catalyst surfaces were derived.

• Bulletin of the Korean Chemical Society
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• v.25 no.4
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• pp.480-484
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• 2004

$LiGaO_2$ films have been grown on Si (100) substrates using a new single precursor $[Li(OCH_2CH_2OCH_3)_2-Ga(CH_3)_2]_2$ under high vacuum conditions $(5{\times}10^{-6}Torr)$. The $[Li(OCH_2CH_2OCH_3)_2Ga(CH_3)_2]_2$ was synthe-sized and characterized by using spectroscopic methods and single-crystal X-ray diffraction analysis. The chemical composition, crystalline structure, and morphology of the deposited films were investigated by X-ray photoelectron spectroscopy, X-ray diffraction, and scanning electron microscopy. The results show that polycrystalline $LiGaO_2$ films preferentially oriented in the [010] direction can be deposited on Si (100) at 500-550$^{\circ}C$ by metal organic chemical vapor deposition (MOCVD). The single precursor $[LiOCH_2CH_2OCH_3)_2-Ga(CH_3)_2]_2$ has been found suitable for chemical vapor deposition of $LiGaO_2$ thin films on Si substrates.

• Korean Journal of Pharmacognosy
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• v.37 no.4 s.147
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• pp.290-293
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• 2006

Phytochemical investigation of the seed extract of Nelumba nucifera Gaerth (Nymphaeaceae) resulted in the isolation of a plant hormon, dihydrophaseic acid (1), a abscisic acid derivative. The chemical structure of 1 was elucidated by 2D-NMR spectroscopic analysis, COSY, DEPT, HMQC and HMBC.