• Bulletin of the Korean Chemical Society
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• v.23 no.9
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• pp.1321-1324
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• 2002

• Bulletin of the Korean Chemical Society
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• v.33 no.1
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• pp.153-158
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• 2012

The hydrogenation of $AlB_2$-type BaGaGe exhibits a metal to insulator (MI) transition, inducing a puckering distortion of the original hexagonal [GaGe] layers. We investigate the electronic structure changes associated with the hydrogen-induced MI transition, using extended H$\ddot{u}$ckel tight-binding band calculations. The results indicate that hydrogen incorporation in the precursor BaGaGe is characterized by an antibonding interaction of $\pi$ on GaGe with hydrogen 1s and the second-order mixing of the singly occupied antibonding $\pi^*$ orbital into it, through Ga-H bond formation. As a result, the fully occupied bonding $\pi$ band in BaGaGe changes to a weakly dispersive band with Ge pz (lone pair) character in the hydride, which becomes located just below the Fermi level. The Ga-Ge bonds within a layered polyanion are slightly weakened by hydrogen incorporation. A rationale for this is given.

• Bulletin of the Korean Chemical Society
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• v.17 no.12
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• pp.1117-1123
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• 1996

Chiral recognition models for resolving π-basic N-acyl-α-(1-naphthyl)alkylamines and π-acidic N-(3,5-dinitrobenzoyl)-α-amino alkyl esters on a (S)-tyrosine-derived chiral stationary phase (CSP) containing both π-basic and π-acidic interaction site have been proposed. In the models, the CSP was supposed to interact with the analytes through the π-π interaction between the 3,5-dinitrophenyl or the 3,5-dimethylphenyl group of the CSP and the 1-naphthyl or the 3,5-dinitrophenyl group of the analyte, and through the hydrogen bonding interaction between the appropriate N-H hydrogen of the CSP and the appropriate carbonyl oxygen of the analyte. In this instance, the alkyl substituent of the pertinent enantiomer of the analyte was found to intercalate between the adjacent strands of the bonded phase and consequently control the trends of the separation factors.

• Bulletin of the Korean Chemical Society
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• v.34 no.5
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• pp.1441-1444
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• 2013

Hetero-dimer anions of naphthalene (Np), anthracene (An), phenanthrene (Ph) and pyrene (Py) were investigated using the time-of-flight mass spectrometer (TOF-MS), anion photoelectron spectroscopy (PES) and theoretical calculation. There are two possible geometries with their electron affinity (EA) difference: parallel displaced (PD) and T-shaped. Dispersion force plays a key role in PD structure with the formation of a new anionic core while ${\pi}$-hydrogen interaction plays a key role in T-shaped structure with the monomer anionic core. The optimized structures and charge distributions can simply be explained by the relative difference of EA.

• Bulletin of the Korean Chemical Society
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• v.4 no.3
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• pp.123-127
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• 1983

The crystal structure of metoclopramide, $C_14H_22ClN_3O_2$, has been determined by X-ray diffraction techniques using diffractometer data obtained by the ${\omega}-2{\theta}$ scan technique with Mo $K\alpha$ radiation from a crystal with space group symmetry $P{\overline{1}}$ and unit cell parameters a = 7.500(1), b = 8.707(2), c = 13.292(2) ${\AA}$; ${\alpha}$ = 101.70(2), ${\beta}$ = 81.20(2), and ${\gamma}$ = $114.90(l)^{\circ}$. The sructure was solved by direct methods and refined by full-matrix least-squares to a final R = 0.055 for the 1524 observed reflections. The bent overall-conformation of the molecule seems to be determined mainly by the bifurcated intramolecular hydrogen bond from the amide nitrogen atom to the methoxy oxygen and the amine nitrogen atoms. The crystal packing consists of the hydrogen bonds, ${\pi}-{\pi}$ interaction and hydrophobic interaction.

• Journal of the Korean Applied Science and Technology
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• v.29 no.2
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• pp.278-285
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• 2012

Effects of ion species on the expansion behavior of Poly(styrene sufonic acid)(PSSA) hydrogel were investigated in aqueous solution of selected anions, cations and hydrophobic ions. The deexpansion extent of Poly(stylene sulfonic acid) gel follow the sequence $SCN^-$<$Br^-$<$Cl^-$<$F^-$ in low concentration solutions due to the destabilization of anions to hydrogen bond between ${SO_3}^-$ and water. The deexpansion in cations followed the sequence of counterion interactions between ${SO_3}^-$ and cations. It was discussed the effects of ions on the hydrogen bonding through ${SO_3}^-$ and phenyl ring in salt solutions. Other interactions, such as the cation-${\pi}$ interaction, hydrophobic interaction, and dispersion force, contributed to the ion specific swelling of PSSA hydrogel.

• Applied Chemistry for Engineering
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• v.9 no.2
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• pp.185-192
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• 1998

Four kinds of polyamicacids(PAAs) were prepared by the condensation reaction of four diamines with different linkages, 3,3'-diaminodiphenyl sulfone(3,3'-$DDSO_2$), 4,4'-diaminodiphenyl sulfone(4,4'-$DDSO_2$), 4,4'-methylene dianiline(4,4'-MDA) and 4,4'-oxydianiline(4,4'-ODA), and dianhydride, 3,3', 4,4'-benzophenone tetracarboxylic dianhydride (BTDA) using the solvent, dimethylacetamide(DMAc). These four PAAs were blended with poly[2,2-(m-phenylene)-5,5'-bibenzimidazole](PBI) from the solution blending. Then called as Blend-I, II, III, and IV, respectively. Cast films or precipitated powders of the PBI/PAA blends were cured at a higher temperature than expected Tg to transform into PBI/PIs blends. Miscibility, specific intermolecular interaction for miscibility and their relative strength as a function of polyimide chemical structure with different four diamines in the PBI/PI systems were investigated. Four blends used in this study were all miscible, and the specific intermolecular interactions existing in these blends was thought to be the hydrogen bonding between the N-H of PBI and the C=O of PIs. The hydrogen bonding in the blends were shown to be stronger in the Blend-III and Blend-IV than Blend-I and II. It is speculated that the differences of hydrogen bonding strength of PBI/PI blends are dependent upon chemical structures of PIs, that is, PIs consisting of $SO_2$ group have a weaker hydrogen bonding strength than those of O or $CH_2$ group because the former has a larger spacer than the latter.

• Journal of the Korean Chemical Society
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• v.29 no.1
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• pp.45-51
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• 1985

Rate constants and activation parameters for the methanolysis of t-butyl halide (t-BuCl, t-BuBr, t-BuI) in various MeOH-DMSO mixtures were measured by conductometric method. Taft's solvatochromic parameters, such as polarity-polarizability(SPP's), ${\pi}^{\ast}$, hydrogen bond donor (HBD) acidity, ${\alpha}$, and hydrogen bond acceptor (HBA) basicity, ${\beta}$ of the solvents, were determined by the so called solvatochromic method using five indicators. The variation of methanolysis rate with the solvent composition was discussed on the basis of the activation parameters and the correlation of the rates with the solvatochromic parameters. It is concluded that the polarity-polarizability, HBD acidity and HBA basicity of the mixtures had an effect on the ionization of t-butyl halide cooperatively, also that the specific interaction between the leaving groups and the solvents, such as ion-dipole and hydrogen bond acceptor-donor interaction, is the most important factor of solvent effects on the stabilization of transition states.

• Journal of the Korean Chemical Society
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• v.19 no.4
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• pp.233-239
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• 1975

The configuration of two oxime groups in cis-2-butenedialdioxime, unsymmetrical compound conjugated by three double bonds, is determined by a NMR study on the effects of the solvent, temperature and concentration; it is certain that, in solutions of usual conditions, the configuration exists as only "syn-syn". And the relative strengths of the hydrogen bond between these oxime groups and several solvents are compared and somc effects of the temperature and concentration are also considered. The several models of hydrogen bond between oxime and solvents are proposed; especially it is to be noted here that the hydrogen bond in pyridine solvent is not resulted from the interaction between a lone electron pair on nitrogen atom of pyridine and the hydroxyl proton of oxime, but the result of $\pi$-complex formed between the $\pi$-orbital of pyridine and the hydroxyl proton of the solute.

• Bulletin of the Korean Chemical Society
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• v.14 no.1
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• pp.101-107
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• 1993

Ab initio calculations are carried out at the 6-311G$^{**}$ level for the $C_{2v}$ interactions of Be and Li atoms with acetylene molecule. The main contribution to the deep minima on the $^3B_2\;BeC_2H_2\;and\;^2B_2 LiC_2H_2$ potential energy curves is the b_2\;(2p(3b_2)-l{\pi}_g^*(4b_2))$ interaction, the $a_1\;(2s(6a_1)-I{\pi}_u(5a_1))$ interaction playing a relatively minor role. The exo deflection of the C-H bonds is basically favored, as in the $b_2$ interaction, due to steric crowding between the metal and H atoms, but the strong in-phase orbital interaction, or mixing, of the $a_1$ symmetry hydrogen orbital with the $5a'_1,\;6a'_1,\;and\;7a'_1$ orbitals can cause a small endo deflection in the repulsive complexes. The Be complex is more stable than the Li complex due to the double occupancy of the 2s orbital in Be. The stability and structure of the $MC_2H_2$ complexes are in general determined by the occupancy of the singly occupied frontier orbitals.