• Title/Summary/Keyword: 방향족성

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MO Theoretical Studies on Nature and Reality of (Y-방향족성의 본질과 존재에 대한 분자궤도론적 연구)

  • Ikchoon Lee;Bon-Su Lee;Chan Kyung Kim
    • Journal of the Korean Chemical Society
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    • v.29 no.4
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    • pp.356-364
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    • 1985
  • Ab initio calculations with STO-3G method were carried out on isomers of isobutylene dianion and dilithioisobutylene, and geometry, energy and Mulliken population were discussed. Energy of reaction, ${\Delta}$E, for isodesmic processes involving these species and relative heats of formation, ${\Delta}H_f$, estimated with ${\Delta}$E have shown that the contribution of "Y-aromaticity" to the structural stabilization of Y-type dianion is a tenuous one but the alkylation appears to proceed via the Y-type dilithio compound.

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Low Temperature NMR Study on p-Fluorophenylthioxanthylium Ions (저온상태에서 NMR을 이용한 p-Fluorophenylthioxanthylium 양이온에 관한 연구)

  • Yang-Soo Ahn;Jung-Hyu Shin
    • Journal of the Korean Chemical Society
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    • v.26 no.3
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    • pp.165-171
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    • 1982
  • The thioxanthylium ion ard anthracenium ion have coplanar geometries. The empty $P_z$-orbitals of the positive centers in the cations, therefore, overlap with the ${\pi}$-orbitals of the fused benzen rings. These cations have aromatic characters, obeying Huckel's (4n + 2)${\pi}$ rule. The contribution of the sulfur atom to aromatic stabilization was estimated by comparing the ${^19F}$-nmr chemical shifts of the thioxanthylium ions and anthracenium ions.

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Separation of Functionalized Heterocyclic Compounds by High Performance Liquid Chromatography (II) (고성능 액체 크로마토그래피에 의한 기능성 헤테로 고리 화합물의 분리(II))

  • Cho, Yun Jin;Lee, Young Cheol;Lee, Kwang-PiII;Park, Keung-Shik
    • Analytical Science and Technology
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    • v.11 no.4
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    • pp.292-296
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    • 1998
  • Normal phase or reversed phase liquid chromatographic separation of isoquinoline of heterocyclic compounds and structural isomers of external substituents, $COOCH_3$, CN and $CH_3$ has been carried out by using several different columns and various mobile phases. From this results, the order of elution of heterocyclic compounds appears to depend on the solvent effect with kinds of mobile phases. Retention mechanism of normal phase system for 2-methylindoline, 2-methylindole, benzoxazole and benzothiazole was also studied depending on adsorption strength between solute and stationary phase of column. However, retention factors of reversed phase system were found on hydrophobic interaction with solvophobic effect.

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Theoretical Studies on the Structure and Aromaticity of 1H-Indene and Mono-sila-1H-Indene (1H-Indene과 Mono-sila-1H-Indene의 구조와 방향족성에 대한 이론적 연구)

  • Ghiasi, Reza;Monnajemi, Majid
    • Journal of the Korean Chemical Society
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    • v.50 no.4
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    • pp.281-290
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    • 2006
  • The electronic structure and properties of the 1H-indene and mono-sila-1H-indene series have been investigated using basis set of 6-31G(d, p) and hybrid density functional theory. Basic measures of aromatic character derived from structure, molecular orbitals, a variety of magnetic criteria (magnetic isotropic and anisotropic susceptibilities) are considered. Energetic criteria suggest that In(Si7) enjoy conspicuous stabilization. However, by magnetic susceptibility isotropic this system are among the least aromatic of the family: Within their isomer series, In(Si4) is the most aromatic using this criteria. Natural bond orbital (NBO) analysis method was performed for the investigation of the relative stability and the nature of the 8-9 bonds in 1H-indene and mono-sila-1H-indene compounds. The results explained that how the p character of natural atomic hybrid orbital on X8 and X9 (central bond) is increased by the substitution of the C8 and C9 by Si. Actually, the results suggested that in these compounds, the X8-X9 bond lengths are closely controlled by the p character of these hybrid orbitals and also by the nature of C-Si bonds. The magnitude of the molecular stabilization energy associated to delocalization from X8-X9 and to * X8-X9 bond orbital were also quantitatively determined. Molecular orbital (MO) analysis further reveal that all structure has three delocalized MOs and two delocalized MOs and therefore exhibit the aromaticity.

PMO Theory of Orbital Interaction (Part 6). Sigma-Aromatic Orbital Interactions in Heteroatom Analogues of Trimethylene Diradical (궤도간 상호작용의 PMO 이론 (제6보). 트리메틸렌 디라디칼의 헤테로 원자 유사체내에서의 시그마 방향족성 궤도간 상호작용)

  • Lee Ik Choon;Kim Ho Soon;Choi Jae Ho
    • Journal of the Korean Chemical Society
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    • v.29 no.2
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    • pp.98-103
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    • 1985
  • Orbital interactions between two nonbonding orbitals have been investigated for heteroatom analogues of trimethylene diradical using MINDO/3 and STO-3G methods. The results showed that the conformers in which significant ${\sigma}$-aromatic stabilization is involved exhibited level order reversal to $n_-$ below $n_+$ as it was found for trimethylene diradical. Lone pair orbitals (LPO) were found to be stabilized by charge dispersion accompanying vicinal trans $n-{\sigma}^*$ interaction and hydrogen bonding. In systems with different heteroatoms, N and O, the contribution of the LPO of oxygen, $n_O$ was always greater in the lower level whereas that of nitrogen, nN, was greater in the higher level as can be expressed as : $n_{\pm}$(lower) = $n_O{\pm}{\lambda}_Nn_N.\;n_{\pm}(higher)\;=\;n_N{\pm}{\lambda}_On_O$. where ${\lambda}_i$< 1.0

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Theoritical Studies on Structure of 4H-Pyran-4-one and Its Sulfur Analogues (4H-Pyran-4-one과 그의 황 유도체의 구조에 관한 이론적 연구)

  • Ikchoon Lee;Hyeong Yeoun Park;Young Ki Kim
    • Journal of the Korean Chemical Society
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    • v.30 no.6
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    • pp.495-499
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    • 1986
  • Structures of 4H-pyran-4-one(I), 4H-pyran-4-thione(II), 4H-thiapyran-4-one (III), 4H-thiapyran-4-thione(IV) have been determined by MNDO and MINDO/3 methods. Geometries and physicochemical properties, especially the aromaticity, were found to agree well with the results of microwave experiments. The order of aromaticity was found to be (IV) > (III) > (II) > (I), which demonstrated inhibitory effect of strongly electronegative oxygen atom on the electron delocaligation, and the order of dipole moment, (II) > (IV) > (I) > (III), indicated the dominant contribution of the bond length of carbonyl group (C=O or C=S)

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Structural and thermal analysis of electrochemically Li intercalated synthetic graphite (전기 화학적으로 리튬이 층간 삽입된 인조흑연의 구조와 열적 특성 분석)

  • Oh, Won-Chun
    • Analytical Science and Technology
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    • v.14 no.3
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    • pp.197-202
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    • 2001
  • The characteristics of the electrochemically Li intercalated synthetic graphite were determined from the studies with XRD method, DSC and solid $^7Li-NMR$ spectrophotometric analysis. From the results of X-ray diffraction method, it was found that the compounds in the stage 1 structure were predominantly formed. The enthalpy and entropy changes of the compounds can be obtained from the differential scanning calorimetric analysis results. From these results, it was found that exothermic and endothermic reactions of lithium intercalated into synthetic graphite are related to thermal stability of lithium ion between carbon graphene layers. From the $^7Li-NMR$ data, scientific observation found that bands are shift toward higher frequencies with increasing lithium concentration because non-occupied electron shells of Li increased in charge carrier density. Line widths of the Li intercalated synthetic graphite compounds decreased slowly because of non-homogeneous local magnetic order and the random electron spin direction for substituted Li.

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Structure and Bonding of Ni(C6H4-nFn)(CO)2 (C6H4=benzyne, n=1-4) Complexes (Ni(C6H4-nFn)(CO)2 (C6H4=benzyne, n=1-4) 착물의 구조 및 화학결합)

  • Ghiasi, Reza;Hashemian, Saeedeh;Irajee, Oranoos
    • Journal of the Korean Chemical Society
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    • v.55 no.2
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    • pp.183-188
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    • 2011
  • The electronic structure and properties of Ni$(C_6H_{4-n}F_n)(CO)_2$ ($C_6H_4$=benzyne, n=1-4) complexes have been investigated using hybrid density functional B3LYP theory. Both aromatic natures and nucleus independent chemical shift (NICS) of the benzyne rings have been analyzed. Among mono-, di-, and tri-fluorinated complexes, 3-F, 3,6-F, and 4-H are the most stable isomers, respectively. NICS values calculated at the several points above the ring centers are consistent with those based on the relative energies of the complexes. The atoms in molecules (AIM) analysis indicates that Ni-C bond distance is well correlated with the electron density of a ring critical point (${\rho}_{rcp}$) in all species.

Characterization of Humic and Fulvic Acids Extracted from Soils in Different Depth: Proton Exchange Capacity, Elemental Composition and 13C NMR Spectrum (깊이별 토양 휴믹산과 풀빅산의 특성 분석: 양성자교환용량, 원소성분비, 13C NMR 스펙트럼)

  • Shin, Hyun-Sang;Lee, Chang-Hoon;Rhee, Dong-Sock;Chung, Kun-Ho;Lee, Chang-Woo
    • Analytical Science and Technology
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    • v.16 no.4
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    • pp.283-291
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    • 2003
  • Humic and fulvic acids present in soils of different depth were extracted and their acidic functional groups and structural characteristics were analyzed and compared. The purpose of this study was to present a basic data needed to evaluate the effect of humic substances on depth distribution and migrational behaviour of radioactive elements deposited on soil. Acidic functional groups of the humic and fulvic acids were analyzed by pH titration method, and their proton exchange capacity (PEC, $mq\;g^{-1}$) and average $pK_a$ values were obtained. Structural characteristics of the humic and fulvic acids were analyzed using their CPMAS $^{13}C$ NMR spectra and elemental composition data. pH titration data showed that fulvic acids have higher acidic functional group contents ranging from 5.5 to $7.0meq\;g^{-1}$ compared with that of humic acids ($3.8{\sim}4.8meq\;g^{-1}$). From depth profiles, it has been found that PEC values of humic acids in deeper soil (> 8 cm) were higher than those at the surface soils. Elemental compositions (H/C ratio) and spectral features ($C_{arom}/C_{aliph}$ ratio) obtained from CPMAS $^{13}C$ NMR spectra showed that the aromatic character in humic acids was a relatively higher than that of fulvic acids, while lower in carboxyl carbon content. The aromatic character and carboxyl carbon contents of humic acids tend to increase as soil depth increased, but those of fulvic acid showed little differences by the soil depth range.

Isolation and Characterization of Humic Acids Present in the Soils at the Vicinity of Domestic Atomic Power Plants(NPPs) (국내 원자력 발전소 주변 토양 휴믹산의 추출 및 특성 규명)

  • Lee, Chang-Hoon;Shin, Hyun-Sang;Chung, Kun-Ho;Cho, Young-Hyun;Lee, Chang-Woo
    • Journal of Radiation Protection and Research
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    • v.28 no.3
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    • pp.165-172
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    • 2003
  • Humic acids present in the soils at the vicinity of domestic atomic power plants(NPPs), located in Yeongkwang(YK), Uljin(UJ), Kori(KR), Koseong(KS), Wolseong(WS) area were isolated, and characterized using elemental analysis and UV/Vis, IR, CPMAS $^{13}C$ NMR spectroscopic methods. The characteristics were compared with one another and with commercial humic acid (Aldrich Co.). Molecular size distributions of the humic acids were determined using a stirred cell ultrafiltration technique. The results of elemental analysis showed that soil humic acid from UJ contains higher oxygen content than humic acids from KR and KS (O/C ratios: 0.51 (UJHA) us. 0.45(KRHA), 0.43(KSHA)). The molecular size distribution revealed that the soil humic acids of UJ and YK contained a higher percentage of larger molecules of > 30,000 daltons, compared to those of KR and KS. The spectral features obtained from UV/vis., IR and CPMAS $^{13}C$ NMR showed that the aromatic character and oxygen containing functional groups in the humic acids from UJ and YK were relatively higher than those of KR and KS. These results indicate that the soil humic acids from UJ and YK were in a higher degree of humification, which may suggest higher affinity of the humic acids with radionuclides released in the soil environments.