• Bulletin of the Korean Chemical Society
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• 제33권12호
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• pp.4098-4102
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• 2012

The potential energy surface (PES) for the loss of HCN from the pyrimidine molecular ion has been explored using quantum chemical calculations. Possible reaction pathways to form five $C_3H_3N^{+{\bullet}}$ isomers have been obtained with Gaussian 4 model calculations. The rate constant for the HCN loss and the product branching ratio have been calculated using the Rice-Ramsperger-Kassel-Marcus theory on the basis of the obtained PES. The resultant rate constant agrees with the previous experimental result. By a kinetic analysis, it is proposed that the formation of $CH=CHC{\equiv}NH^{+{\bullet}}$ is favored near the dissociation threshold, while the formation of $CH=CHN{\equiv}CH^{+{\bullet}}$ is favored at high energies.

• 한국군사과학기술학회지
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• 제6권1호
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• pp.108-115
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• 2003

TNAZ is a high explosive material because it is a highly strained ring compound containing one nitramine and gem dinditro groups. 1-t-butyl-3-nitroazetidine which was used as an intermediate previously, which declined the overall yield in synthesizing TNAZ. We obtained 1-t-butyl-3-hydroxymethyl-3-nitroazetidine in 64% yield from advances process which was used in synthesis of 1-t-butyl-3-nitroazetidine. The reaction pathway, shortening of reaction time, together with improvement of yield were studied too. We have obtained TNAZ in 85% yield.

• Bulletin of the Korean Chemical Society
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• 제4권3호
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• pp.120-123
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• 1983

The reaction of hexacyanoferrate (Ⅲ) with nitrotoluenes in aqueous acetic acid containing perchloric acid(1.0 M) at $50^{\circ}C$ gave the corresponding aldehyde as the major product. The order with respect to each of the reactants ― substrate, oxidant and acid ― was found to be unity. The Hammett plot yielded a ${\sigma}^+$ value of -1.30, and the kinetic isotope effect gave a $k_H/k_D$ value of 6.2. The pathway for the conversion of the nitrotoluenes to the products has been mechanistically visualized as proceeding through the benzylic radical intermediate, formed in the rate determining step of the reaction.

• Bulletin of the Korean Chemical Society
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• 제21권8호
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• pp.823-827
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• 2000

Gas-Phase reactions of methyl and ethyl nitrites with anionic nucleophiles of SH-, F- and OH- are investigated theoretically at the MP2/6-311+G* level. The SN2 processes are all highly exothermic and proceed with a typ-icaI double-weIl reaction coordinate profile. The elimination reactions of methyl nitrite with SH- and F- are double-well energy surface processes,with stabilizedproduct complexes of NO-...H2S and NO-...HF, pro-ceeding by an E1 cb-like E2 mechanism. The $\beta-elimination$ of ethyl nitrite is an E2 type process. The $\alpha-elimi-nation$ reactions of methyl and ethyl nitrites with OH- have triple-well energy profiles of Elcb pathway with an $\alpha-carbanion$ intermediate which is stabilized bythe vicinal $nc\alpha-{\sigma}*o-N$ charge transfer interactions. CompIex-ation ofmethyl carbanion with HF seems to provide a stable intermediate within a triple-well energy profile of El cb channel in the reaction of F- with methyl nitrite.

• Bulletin of the Korean Chemical Society
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• 제13권4호
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• pp.395-398
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• 1992

Rate of solvolysis of dansyl chloride in aqueous binary mixtures of acetone, methanol and ethanol are reported. Kinetic solvent isotope effects in methanol and product selectivities in alcohol-water mixtures are also reported. Kinetic data are interpreted with the Grunwald-Winstein and Kivinen equations. The value of $k_{CH3OH}/k_{CH3OD}=1.76$ suggests that a general have catalyzed and/or an $S_AN$ pathway is operative in methanol, a less polar solvent. Rate-rate profiles for solvolysis of dansyl chloride in the aqueous binary media indicate a change in reaction channel from $S_AN$ (in less polar media) to $S_N2$ (in more polar media) mechanism.

• Bulletin of the Korean Chemical Society
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• 제17권3호
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• pp.254-257
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• 1996

Nucleophilic substitution reactions of 1- and 2-naphthylethyl arenesulfonates, 2 and 3, with anilines and benzylamines in methanol at 65.0 ℃ are investigated. The rates are slower than those for the corresponding derivatives of 2-phenylethyl arenesulfonates, 1, which can be attributed to a greater degree of positive charge stabilization at Cα in the transition state (TS) by a greater electron supply from a phenyl ring compared to a naphthyl ring. The mechanism for the two naphthylethyl systems are similar to that for the 2-phenylethyl derivatives, except that the transition state is formed at somewhat an earlier position along the reaction coordinate. The secondary kinetic isotope effects involving deuterated nucleophilies indicate that naphthylethyl series are sterically more crowded in the TS than 2-phenylethyl system. The data in this work can not elucidate the possible participation of the aryl-assisted pathway in the reaction.

• Bulletin of the Korean Chemical Society
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• 제18권3호
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• pp.324-327
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• 1997

Water soluble iridium complex, IrCl(CO)(TPPTS)2·χH2O (1) (TPPTS=m-trisulfonated triphenylphosphine) has been prepared from the reaction of a water soluble complex, IrCl(COD)(TPPTS)2·6H2O (COD=l,5-cyclooctadiene) with CO and unambiguously characterized by electronic absorption, 31P NMR, 13C NMR and IR spectral data. Complex 1 catalyzes the hydration of terminal alkynes to give ketones in aqueous solutions at room temperature. The rate of PhC≡CH hydration dramatically increases with addition of MeOH to the reaction mixture in H2O, which is understood in terms of i) the excellent miscibility between H2O and MeOH and ii) the assumed catalytic hydration pathway involving the initial formation of (alkyne)IrCl(CO)(TPPTS)2.

• 대한화학회지
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• 제68권2호
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• pp.87-92
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• 2024

The commercialization of rechargeable metal-air batteries is extremely desirable but designing stable oxygen reduction reaction (ORR) catalysts with non-noble metal still has faced challenges to replace platinum-based catalysts. The nonnoble metal catalysts for ORR were prepared to improve the catalytic performance and stability by the thermal decomposition of ZIF-8 with optimum cobalt loading. The porous carbon was obtained by the calcination of ZIF-8 and different loading amounts of Co nanoparticles were anchored onto porous carbon forming a Co/PC catalyst. Co/PC composite shows a significant increase in the ORR value of current and stability (500 h) due to the good electronic conductive PCN support and optimum cobalt metal loading. The significantly improved catalytic performance is ascribed to the chemical structure, synergistic effects, porous carbon networks, and rich active sites. This method develops a new pathway for a highly active and advantageous catalyst for electrochemical devices.

• Animal Bioscience
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• 제34권6호
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• pp.993-1005
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• 2021

Objective: Zearalenone (ZEA) has estrogen-like effects. Our previous study has shown that ZEA (0.5 to 1.5 mg/kg) could induce abnormal uterine proliferation through transforming growth factor signaling pathway. To further study the other regulatory networks of uterine hypertrophy caused by ZEA, the potential mechanism of ZEA on porcine endometrial epithelial cells (PECs) was explored by the Illumina Hiseq 2000 sequencing system. Methods: The PECs were treated with ZEA at 0 (ZEA0), 5 (ZEA5), 20 (ZEA20), and 80 (ZEA80) µmol/L for 24 h. The collected cells were subjected to cell cycle, RNA-seq, real-time quantitative polymerase chain reaction, immunofluorescence, and western blot analysis. Results: The proportion of cells in the S and G2 phases decreased (p<0.05), but the proportion of cells in the G1 phase increased (p<0.05) in the ZEA80 treatment. Data analysis revealed that the expression of Wnt pathway-related genes, estrogen-related genes, and mitogen-activated protein kinase pathway-related genes increased (p<0.05), but the expression of genetic stability genes decreased (p<0.05) with increasing ZEA concentrations. The relative mRNA and protein expression of WNT1, β-catenin, glycogen synthase kinase 3β (GSK-3β) were increased (p<0.05) with ZEA increasing, while the relative mRNA and protein expression of cyclin D1 (CCND1) was decreased (p<0.05). Moreover, our immunofluorescence results indicate that β-catenin accumulated around the nucleus from the cell membrane and cytoplasm with increasing ZEA concentrations. Conclusion: In summary, ZEA can activate the Wnt/β-catenin signaling pathway by up-regulating WNT1 and β-catenin expression, to promote the proliferation and development of PECs. At the same time, the up-regulation of GSK-3β and down-regulation of CCND1, as well as the mRNA expression of other pathway related genes indicated that other potential effects of ZEA on the uterine development need further study.

• Asian-Australasian Journal of Animal Sciences
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• 제13권6호
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• pp.748-756
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• 2000

Effects of xanthine (X), xanthine oxidase (XO), and catalase (C), $H_2O_2$, and carbohydrates on sperm capacitation, acrosome reaction, and fertilizing ability in vitro were examined. Glucose alone, but not fructose, supported the maximum rate of sperm capacitation and acrosome reaction. However, in the combination of X, XO, and C (XXOC) or $H_2O_2$, fructose alone also supported maximum capacitation, acrosome reaction, and fertilization. Either insufficient or excessive amounts of $H_2O_2$ decreased sperm capacitation and the acrosome reaction. In order to understand how glucose generates $H_2O_2$ or other reactive oxygen species in sperm cells, 6-aminonicotinamide, an inhibitor of the pentose-phosphate pathway (PPP), and apocynin, an inhibitor of NADPH oxidase, were added to sperm suspensions in glucose-containing medium. Results appeared that sperm capacitation, acrosome reaction, and fertilization were consequently inhibited by either one of these compounds. These inhibitory effects were nullified by addition of XXOC. These results support the hypothesis that glucose, in addition to being a substrate for glycolysis, facilitates sperm capacitation and the acrosome reaction by generating reactive oxygen species through G-6-P dehydrogenase and NADPH oxidase.