• Bulletin of the Korean Chemical Society
• /
• 제29권6호
• /
• pp.1195-1198
• /
• 2008

Kinetic studies of the additions of benzylamines to a noncyclic dicarbonyl group activated olefin, methyl $\alpha$-acetyl-$\beta$ -phenylacrylates (MAP), in acetonitrile at 30.0 ${^{\circ}C}$ are reported. The rates are lower than those for the cyclic dicarbonyl group activated olefins. The addition occurs in a single step with concurrent formation of the $C_\alpha$ -N and $C_\beta$ -H bonds through a four-center hydrogen bonded transition state. The kinetic isotope effects ($k_H/k_D$ > 1.0) measured with deuterated benzylamines ($XC_6H_4CH_2ND_2$) increase with a stronger electron acceptor substituent ($\delta\sigma$ X > 0) which is the same trend as those found for other dicarbonyl group activated series (1-4). The sign and magnitude of the cross-interaction constant, ρXY, is comparable to those for the normal bond formation processes in the $S_N2$ and addition reactions. The relatively low ${\Delta}H^\neq$ and large negative ${\Delta}S^\neq$ values are also consistent with the mechanism proposed.

• 한국결정학회지
• /
• 제5권2호
• /
• pp.100-107
• /
• 1994

분자내 (2+2) 광고리화 반응을 통하여 pyridine의 새로운 N1-pentenyl유도체가 얻어졌다. 이 물질의 구조는 단 결정 X-선 회절법에 의해 해석되었다. 이 화합물은 rhombohedral계( R3, a=27.767(5)A, c=6.390(2)A)로 결정화된다. 이 구조에서는 2개의 6각 고리와 1개의 4각 고리가 N-C 또는 C-C bonds를 공유하면서 fuse되어 있고, pyridine고리는 의자모양의 형태를 취하고 있다. 점대칭으로 연관된 한 쌍의 분자들이 uracil 부분의 N,0 원자 사이의 H를 통하여 수소결합을 생성하고 있는 것이 관찰되었다.

• 대한화학회지
• /
• 제50권5호
• /
• pp.369-373
• /
• 2006

Pd(CF3CO2)2-phosphine 및 Pd(CF3CO2)2-sulfide 계를 촉매로 사용하여 styrene의 아릴화반응을 연구하였다. 주 생성물인 trans-stilbene의 수율은 phosphine 치환체의 염기도가 증가할수록 높아졌고 입체장애가 클수록 낮아졌다. arylphosphine에서 styrene으로 aryl 기가 이동하는 현상은 동일한 arylphosphine에 대하여 Pd(CF3CO2)2의 경우가 더 높은 염기도를 가진 Pd(CH3CO2)2의 경우보다 더 많이 나타났으므로 이 반응은 Pd 이온이 먼저 aryl 기에 공격을 하는 친전자성 메커니즘에 의해 진행된다고 본다. 한편 Pd(CF3CO2)2-sulfide보다 Pd(CF3CO2)2-phosphine 계가 더 효과적인 촉매로 작용하였다.

• BMB Reports
• /
• 제32권3호
• /
• pp.288-293
• /
• 1999

In order to understand the initial interaction of the substrates malonate, ATP, and CoA with malonyl-CoA synthetase, the catalytic product malonyl-CoA was characterized by NMR spectroscopy and molecular modeling. To assign proton and carbon chemical shifts, two-dimensional $^1H-^1H$ DQF-COSY and $^1H-^{13}C$ HMBC experiments were used. The structure of malonyl-CoA in the solution phase was determined based on distance constraints from NOESY and ROESY spectra. The structures were well-converged around the pantetheine region with the pairwise RMSD value of 0.08 nm. The solution structure exhibited a compact folded conformation with intramolecular hydrogen bonds among its carbonyl and hydroxyl groups. These findings will help us to understand the initial interaction of malonate and CoA with malonyl-CoA synthetase.

• 센서학회지
• /
• 제16권2호
• /
• pp.97-103
• /
• 2007

Crystallized carbon nitride film that has many stable physical and/or chemical properties has been expected potentially by a new electrical material. However, one of the most significant problems degrading the quality of carbon nitride films is an existence of N-H and C-H bonds from the deposition environment. The possibility of these reactions with hydroxyl group in carbon nitride films, caused by a hydrogen attack, was suggested and proved in our previous reports that this undesired effect could be applied for fabricating micro-humidity sensors. In this study, MIS capacitor and MIM capacitor with $5{\mu}m{\times}5{\mu}m$ meshes were fabricated. As an insulator, carbon nitride film was deposited on a $Si_{3}N_{4}/SiO_{2}/Si$ substrate using reactive magnetron sputtering system, and its dielectric constant, C-V characteristics and humidity sensing properties were investigated. The fabricated humidity sensors showed a linearity in the humidity range of 0 %RH to 80 %RH. These results reveal that MIS and MIM $CN_{X}$ capacitive humidity sensors can be used for Si based micro-humidity sensors.

• 한국염색가공학회지
• /
• 제22권2호
• /
• pp.83-87
• /
• 2010

Crystal structure of coumarin 6 has been solved by X-ray diffraction. The crystals are triclinic, space group P-1, with a=8.823(2) ${\AA}$, b=8.898(2) ${\AA}$, c=11.025(9) ${\AA}$, ${\alpha}$=86.41(3)$^{\circ}$, ${\beta}$=85.39(3)$^{\circ}$, ${\gamma}$=76.23(3)$^{\circ}$, Mr=350.42, V=837.1(3) ${\AA}^3$, Z=2 and R=0.0516. The molecules are packed parallel to each other by weaker ${\pi}{\cdots}{\pi}$ and C-H${\cdots}{\pi}$ interactions. The detailed geometry of C-H${\cdots}{\pi}$ interactions were discussed. The hydrogen bonds and non-traditional C-H${\cdots}O$ interactions join the no-parallel molecules together. All the molecules packed wall-like with the molecular brick.

• 대한방사성의약품학회지
• /
• 제5권2호
• /
• pp.101-112
• /
• 2019

Herein, 2-nitroimidazole-fluorophore conjugates were synthesized by linking 2-nitroimidazole and FITC or RITC via thiourea bonds. The prepared derivatives were stable for 2 h in Dulbecco's modified Eagle's medium (DMEM) at 37 ℃. The novel conjugates were studied for their in vitro uptake under hypoxic conditions using U87MG and CT-26 cell lines, showing significantly higher uptakes in hypoxic than normoxic cells. Immunohistochemical analysis confirmed hypoxia in U87MG and CT-26 xenografted tumor tissues. Moreover, the prepared conjugates were evaluated by in vivo experiments after intravenous injection in U87MG and CT-26 xenografted mice. Hypoxia was confirmed by immunohistochemistry of the prepared derivatives with co-injected pimonidazole. Confocal microscopy of the prepared derivatives showed strong fluorescence in hypoxic tumor tissues correlated with the pimonidazole distribution. This suggested that the 2-nitroimidazole-fluorophore conjugates are promising optical imaging probes for tumor hypoxia and are promising substitutes for pimonidazole immunohistochemistry, which requires a multi-step procedure of incubation involving antibody, second antibody, dye, hydrogen peroxide, and multiple washing steps.

• 한국근적외분광분석학회:학술대회논문집
• /
• 한국근적외분광분석학회 2001년도 NIR-2001
• /
• pp.1287-1287
• /
• 2001

The structure of water molecules in the pure liquid state has been subjected to extensive research for several decades. Questions still remain unanswered, however, and no single model has been found capable of explaining all the anomalies of water. In the present study near-infrared spectra of water in the temperature region 6-$80^{\circ}C$ have been analysed by use of principal component analysis (PCA) and two-dimensional correlation spectroscopy in order to study the dynamic behaviour of the water band centred at 1440 nm, which is due to the combination of symmetric and antisymmetric O-H stretching modes. It has been found that the wavelengths 1412 and 1491 nm account for more than 99% of the spectral variation, representing two major water species with weaker and stronger hydrogen bonds, respectively. A third species located at 1438 nm, whose concentration was relatively constant as a function of temperature, is also indicated. A somewhat distorted two-state structural model for water is suggested.

• Bulletin of the Korean Chemical Society
• /
• 제32권6호
• /
• pp.1851-1858
• /
• 2011

Details of the double-bond isomerization of 1-hexene over H-ZSM-5 were clarified using density functional theory. It is found that the reaction proceeds by a mechanism which involves the Br${\o}$nsted acid part of the zeolite solely. According to this mechanism, 1-hexene is first physically adsorbed on the acidic site, and then, the acidic proton transfers to one carbon atom of the double bond, while the other carbon atom of the double bond bonds with the Br${\o}$nsted host oxygen, yielding a stable alkoxy intermediate. Thereafter, the Br${\o}$nsted host oxygen abstracts a hydrogen atom from the $C_6H_{13}$ fragment and the C-O bond is broken, restoring the acidic site and yielding trans-2-hexene. The calculated activation barrier is 12.65 kcal/mol, which is in good agreement with the experimental value. These results well explain the energetic aspects during the course of double-bond isomerization and extend the understanding of the nature of the zeolite active sites.

• 한국식품영양학회지
• /
• 제11권5호
• /
• pp.499-505
• /
• 1998

The purpose of this study was to ivestigate the structural characteristics of waste soulble browning reaction prodcuts (WS-BRPs) isolated from Korean red ginseng. They all showed the maximum absorbances at near 280 nm. Their IR spectra suggested the presence of hydroxyl, amide carbonyl and aliphatic methine groups. From sugar analysis it was identified that L and S-1 contained two kinds of suggar, glucose and xylose, and S-2, a fructose together with glucose and xylose. Thirteen different amino acids were identified in L. Ten amino acids from S-1 and seven amino acids from S-2 were identified using Auto Amino Acid Analyzer. Glycine, serine and glutamic acid in S-1 and one unknown amino acid and glycine in S-2 were detected as the major amino acids, respectively. From the 1H-and 13C-NMR spectra, it was identified that a number of sugar moieties, carbonyl and carbon double bonds (only in S-2) were contained in the three WS-BRP components. Approximate number of sugar moiety of L, S-1 and S-2 was determined to be 8∼10, 9∼11 and 4∼5, respectively. Contents of nitrogen, carbon and hydrogen showed L>S-1>S-2.