• Bulletin of the Korean Chemical Society
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• 제32권6호
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• pp.2063-2069
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• 2011

We studied the interaction of 3,3',3'',3'''-ethylenetetrakis-4-hydroxycoumarin (EHC) with bovine serum albumin (BSA) in acetate buffer and phosphate buffer with different pH values by UV-vis absorption spectrometry and fluorescence spectrometry respectively. It was found that the pH values of the buffer solutions had an effect on the interaction process. In acetate buffer of pH 4.70, the carbonyl groups in EHC bound to the amino groups in BSA by means of hydrogen bond and van der Waals force, which made the extent of peptide chain in BSA changed. By contrast, in phosphate buffer of pH 7.40, hydrophobic force played a major role in the interaction between EHC and BSA, while the hydrogen bond and van der Waals force were also involved in the interaction. The results of spectrometry indicated that BSA could enhance the fluorescence intensity of EHC by forming a 1:1 EHC-BSA fluorescent complex through static mechanism at pH 4.70 and 7.40 respectively. Furthermore, EHC bound on site 1 in BSA.

• 한국세라믹학회지
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• 제42권5호
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• pp.304-307
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• 2005

The possible configurations of hydroxyl group in hexagonal hydroxyapatite were identified through molecular orbital calculation. The molecular orbital interaction between O and H in hydroxyl column was analyzed using charge variation and Bond Overlap Population (BOP). We supposed 5 kinds of O-H bond configurations as cluster types of I, II, III, IV, and V. Mulliken's population analysis was applied to evaluate ionic charges of O, H, P, and Ca ions, and BOPs (Bond Overlap Populations) in order to discuss the bond strength change by the atomic arrangement. The stability of each O-H bond configuration was analyzed using bond overlap and ionic charge.

• Bulletin of the Korean Chemical Society
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• 제20권4호
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• pp.445-450
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• 1999

Molecular dynamics (MD) simulation of non-rigid H-Y zeolite framework are performed at 298.15 and 5.0 K. Usual bond stretching, bond angle bending, torsional rotational, and non-bonded Lennard-Jones and electrostatic interactions are considered as intraframework interaction potentials. Calculated atomic parameters are in good agreement with the experiment, which indicates the successful reproduction of the framework structure and its motion. Both calculated bond lengths and bond angles are also in good agreement with the experiment except generally for a little longer bond lengths and a little smaller T-O-H bond angles. The calculated overall site occupation of HI keeps the order O(2) > O(3) > O(4) > O(t) at 298.15 K, which is very different from the experimental prediction, O(l) > O(3) > O(2) at 5 K. Calculated IR spectra of the H-Y zeolite framework show that most of the main peaks of the O-H bonds are in the broad region 3700-5000 cm-1 and that the O-T stretching bands appeared in 0-2000 cm-1 and at 2700 cm-1

• 한국세라믹학회지
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• 제46권4호
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• pp.425-428
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• 2009

We performed a density functional theory study to investigate the interaction of DEMS (diethoxymethylsilane) with the H-terminated Si (001) surface. The optimum structure of DEMS was first calculated by a first principles study. The dissociation probability of the O-C bond of DEMS was higher than the other seven bonds based on the bond energy calculation. When the fragmented DEMS groups reacted with the H-terminated Si (001) surface, it was the most favorable among the eight reactions to form a bond between the Si atom on the surface and the O atom of a fragmented DEMS group (($C_2H_5O$)Si($CH_3$)(H)-O-) by forming a $C_2H_6$ as by-product.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.487-488
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• 2008

SiOC films containing alkyl groups have a low dielectric constant because of the interaction between the C-H hydrogen bonds and the oxygen of high electro-negative atom. The Si-$CH_3$ in a void is broken by the $O_2$, therefore the strength of CH bond in Si-O-O-$CH_3$ bond increases. The Si-O-O-$CH_3$ bond is broken by nucleophilic attack due to Si atom, again. The elongation of C-H bond causes the red shift, and the compression of C-H bond causes the blue shift. Among these chemical shifts, the blue shift from $1000\;cm^{-1}$ to $1250\;cm^{-1}$ was related with the formation of pores. If the oxygen is deficient condition, the methylradicals of the electron-rich substitution group terminate easily the Si-O-Si cross-link, and the pore is originated from the cross-link breakdown due to much methyl radicals of Si-$CH_3$. The dielectric constant of the films decreases due to pore generation.

• Bulletin of the Korean Chemical Society
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• 제27권4호
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• pp.495-502
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• 2006

Intramolecular energy flow and C-$H_{methyl}$ and C-$H_{ring}$ bond dissociations in vibrationally excited toluene in the collision with HF have been studied by use of classical trajectory procedures. The energy lost by the vibrationally excited toluene upon collision is not large and it increases slowly with increasing total vibrational energy content between 20,000 and 45,000 $cm ^{-1}$. Above the energy content of 45,000 $cm ^{-1}$, however, energy loss decreases. Furthermore, in the highly excited toluene, toluene gains energy from incident HF. The temperature dependence of energy loss is negligible between 200 and 400 K. Energy transfer to or from the excited methyl C-H bond occurs in strong collisions with HF transferring relatively large amount of its translational energy (>> $k_BT$) in a single step, whereas energy transfer to the ring C-H bond occurs in a series of small steps. When the total energy content $E_T$ of toluene is sufficiently high, either C-H bond can dissociate. The C-$H_{methyl}$ dissociation probability is higher than the C-$H_{ring}$ dissociation probability. The dissociation of the ring C-H bond is not the result of the intermolecular energy flow from the direct collision between the ring C-H and HF but the intramolecular flow of energy from the methyl group to the ring C-H stretch. The C-$H_{ring}$${\cdot}{\cdot}{\cdot}$HF interaction is not important in transferring energy and in turn bond dissociation.

• 대한화학회지
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• 제31권1호
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• pp.14-24
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• 1987

실리카 및 제올라이트의 OH기 또는 교환된 양이온과 CO분자간의 상호작용과 전자구조를 살펴보기 위하여 CNDO/2계산을 행하였다. 실리카의 OH기와 CO분자간의 상호작용에너지는 약 12kcal/mol이었고, 그 결합거리, R(O-H${\cdots}$C)는 2.6${\AA}$이었다. 여러가지의 양이온과 CO분자와의 결합강도는 $H^+ < Na^+ < Li^+$의 순이었는데, 그것은 양이온의 정전기적 장의 세기와 일치하였다. 또한 OH기나 양이온과 결합하고 있는 CO분자의 결합차수는 OH-CO type의 경우를 제외하고는 모두 증가하였다. 제올라이트에 있는 양이온을 떼어내는데 필요한 에너지는 $H^+ > Li^+ > Na^+$의 순이었으며, 이것은 제올라이트의 골격으로부터 양이온으로 이동되는 전하의 양과 관계가 있다.

• Bulletin of the Korean Chemical Society
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• 제34권12호
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• pp.3591-3596
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• 2013

The enantioselective aza-Morita Baylis Hillman reaction of nitroalkene and N-tosylimine catalyzed by thiourea-tertiary amine has been investigated using density functional theory. Enantioselectivity is dominated by the cooperative effect of non-covalent and weak covalent interactions imposed by different units of catalyst. As Lewis base, the tertiary amine unit activates nitroalkene via weak covalent bond. The weak covalent interaction orients the reaction in a major path with smaller variations of this bond. The aromatic ring unit activates N-tosylimine via ${\pi}-{\pi}$ stacking. The non-covalent interaction selects the major path with smaller changes of the efficient packing areas. Thiourea unit donates more compact H-bonded network for species of the major path. The calculated ee value in xylene solution phase (97.6%) is much higher than that in N,N-Dimethylformamide (27.2%). Our conclusion is also supported by NBO analysis.

• Bulletin of the Korean Chemical Society
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• 제31권3호
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• pp.595-598
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• 2010

Ab initio and DFT molecular orbital calculations predict that acetyl radical reacts with acetylene through interactions primarily involving the SOMO of the radical and the in-plane ${\pi}$-bond of acetylene. An energy barrier (${\Delta}E_1$) of 39.6 kJ $mol^{-1}$ is predicted for the preferred anti arrangement of reactants at the CCSD(T)/cc-pVDZ//BHandHLYP/cc-pVDZ level of theory. NBO analysis reveals additional interactions between the radical SOMO and the nearby C-H ${\sigma}$-bond in acetylene worth about 10% of the total transition state interaction energy. This type of orbital interaction has not previously been observed in radical addition reactions involving C-C ${\pi}$-bonds.

• Bulletin of the Korean Chemical Society
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• 제23권2호
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• pp.221-224
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• 2002

Nucleophilic addition reactions of benzylamines (BA; $XC_6H_4CH_2NH_2$) to ethyl-${\alpha}$-cyanocinnamates (ECC;$YC_6H_4CH$=C(CN)COOEt) have been investigated in acetonitrile at $30.0^{\circ}C$. The rate is first order with respect to BA and ECC. The rate is slower than that expected from the additive effect of ${\sigma}^-$ or $R^-$ for the activating groups (CN and COOEt). Natural. bond orbital ${\pi}^{\ast}_{c=c}$ calculations show that the contribution of COOEt group may not be fully effective despite the coplanar molecular structure. The selectivity parameters including the cross-interaction constant (${\rho}_{xy}$ = -0.22) indicate that the addition occurs in a single step. The kinetic isotope effects ($k_H/k_D$=2.5-2.8) involving deuterated BA ($XC_6H_4CH_2ND_2$) nucleophiles and activation parameters (${\Delta}H^{\neq}=4{\sim}6\;kcal\;mol^{-1};{\Delta}S^{\neq}=-45{\sim}-52\;e.u.$) suggest a cyclic transition state in which N-$C_{\alpha}$ and H-$C_{\beta}$ bonds are formed concurrently.