• Title/Summary/Keyword: radical reaction sites

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Prediction of Radical Reaction Positions in PAHs by HOMO and LUMO Calculation (HOMO 및 LUMO 계산에 의한 PAHs의 라디칼 반응위치 예측)

  • Lee, Byung-Dae
    • Journal of the Korean Applied Science and Technology
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    • v.27 no.1
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    • pp.1-5
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    • 2010
  • HOMO(the highest occupied molecular orbital) and LUMO(the lowest unoccupied molecular orbital) of four recalcitrant polycyclic aromatic hydrocarbons (PAHs) were calculated by MOPAC program(CaChe Co). The previous papers which reported experimental results about radical reaction of PAHs were reviewed. The reported radical reaction positions of four PAHs corresponded with predicted positions in which ${\Delta}E$(HOMO-LUMO) was high. From these results, it appears that determining the ${\Delta}E$(HOMO-LUMO) of a PAH is a promising method for predicting the radical reaction position.

Synthesis of Quinazoline 4-one Drvivatives from 2-Aminobenzamide(II) - Reaction with $\gamma$-Lactone and Diketone (2-Aminobenzamide로부터 Quinazoline 4-one 유도체의 합성 (II) - $\gamma$-락톤과 디케톤과의 반응)

  • 서명은
    • YAKHAK HOEJI
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    • v.30 no.5
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    • pp.203-207
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    • 1986
  • 2-Aminobenzamide reacts with not only keton radical but also carbonyl group in carboxylic acid, to form easily -N-C-N-novel ring cyclization as a result I and V. In addition, it reacts with 1, 2-cyclohexadione or benzil, whitch are both 1, 2-diketone compounds, at the both ketone radical sites to give V or VII respectively. On the reaction with dimethone, however, which has 1, 3-diketone radical, it reacted with only one carbanyl group and VI was produced. We investigated the reaction with cr-ketoester such as ethyl pyruvate and diethyl rnesoxalate. In the reaction with ethylpyruvate, amine group in 2-aminobenzamide reacted not with ketone radical but carbonyl group in ester (product VIII). On the other hand, diethyl measoxalate reacted at the ketone radical site rather than the ester site (product IX).

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Evaluation of reaction site prediction in 3-ring PAHs according to calculation level

  • Lee, Byung-Dae
    • Journal of the Korean Applied Science and Technology
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    • v.39 no.4
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    • pp.535-541
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    • 2022
  • The radical reaction position was calculated by varying the calculation level for ACEL and ANT, which are detected with the highest frequency and concentration in PAHs pollution sites. The results of each calculation level were compared and evaluated with the existing literature. HF, B3LYP, B3LYP-D, and MP2 were used as the method for each level used for calculation. Except for HF, the MK charge by B3LYP, B3LYP-D, and MP2 was consistent with the experimental results. It was found that the dispersion effect was negligible in the calculation of ACEL and ANT because the calculation results by the B3LYP and B3LYP-D methods were the same. In particular, it was found that the MK charge calculation result by MP2 agrees well with the product/PAH ratio obtained as a result of the experiment. Considering the calculation cost, it would be preferable to use B3LYP to predict the radical reaction site of ACEL and ANT. However, considering the product/PAH ratio, it takes more time to calculate, but it is judged that it is better to use the MP2.

Prediction of Hydroxyl Substitution Site(s) of Phenol, Monochlorophenols and 4-Chloronitrobenzene by Atomic Charge Distribution Calculations

  • Lee, Byung-Dae;Lee, Min-Joo
    • Bulletin of the Korean Chemical Society
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    • v.30 no.4
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    • pp.787-790
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    • 2009
  • The predictions of the radical reaction sites for phenol, 2-, 3- and 4-chlorophenols (CPs) and 4-chloronitrobenzene (CNB) were studied by atomic charge distribution calculations. The atomic charge distributions on each atom of these molecules were obtained using the CHelpG and MK (Merz-Kollman/Singh) methods with the optimized structural parameters determined by DFT calculation at the level of BLYP/6-311++G(d,p). By comparing the experimentally obtained hydroxyl addition site(s) and the calculated atomic charges on carbon atoms of phenol and CPs, we found that hydroxyl substitution by oxidation reaction mainly occurred to the carbon(s) with high atomic charges. With these results, we were easily able to predict the position(s) of the ·OH reaction site(s) of phenol, CPs and CNB through atomic charge distribution calculations.

PARTIAL OXIDATION OF PROPANE ON NAFION SUPPORTED CATALYTIC MEMBRANE

  • F. Frusteri;C. Espro;F. Arena;F. Arena;E. Passalacqua;A.Patti;A. Parmaliana
    • Proceedings of the Membrane Society of Korea Conference
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    • 1999.07a
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    • pp.55-58
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    • 1999
  • Nafion supported catalytic membranes were found to be active, stable and selective in th partial oxidation of propane to oxygenates with H2O2 under mild condition. Addition of Fe2+ in liquid phase enhances the reaction rate. Reaction proceeds according to a radical mechanism based on th electrophilic activation of propane on superacid sites and subsequent reaction of the activated paraffin with OH radicals. The use of a catalytic membrane, which allow separation of the intermediate products from the liquid phase containing the oxidant, was found to be effective to perform selective partial oxidation of propane with high yields to oxygenated products.

New Self-Directed Growth Mechanism of Molecular Lines across the Dimer Rows on H-terminated Si(001) Surface

  • Choi, Jin-Ho;Cho, Jun-Hyung
    • Proceedings of the Korean Vacuum Society Conference
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    • 2011.02a
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    • pp.301-301
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    • 2011
  • We present theoretical investigations of the self-assembled growth of one-dimensional (1D) molecular lines directed across the dimer rows on the H-terminated Si(001) surface [1]. Based on density-functional theory calculations, a new growth mechanism of the 1D acetylacetone line is proposed [2], which involves the radical chain reaction initiated at two dangling-bond sites on one side of two adjacent Si dimers. It is also enabled that, if an H-free Si dimer were employed as the initial reaction site, a 1D acetylacetone line can grow along the dimer row. Our findings represent the first insight into the growth of 1D molecular lines not only across but also along the dimer rows on the H-terminated Si(001) surface.

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Preferential Peroxidase Activity of Prostaglandin Endoperoxide H Synthase for Lipid Peroxides

  • Yun, Seol-Ryung;Han, Su-Kyong;Song, In-Seok
    • Proceedings of the Korean Society of Applied Pharmacology
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    • 2001.11a
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    • pp.94-94
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    • 2001
  • Prostaglandin endoperoxide H synthase (PGHS) catalyzes the committed step in prostaglandins and thromboxane A$_2$-- oxygenation of arachidonic acid to the hydroperoxy endoperoxide PGG$_2$, followed by reduction PGG$_2$to the alcohol PGH$_2$. The two reactions by PGHS -- cyclooxygenase and peroxidase -- occur at distinct but structurally and functionally interconnected sites. The peroxidase reaction occurs at a heme-containing active site located near the protein surface. The cyclooxygenase reaction occurs in a hydrophobic channel in the core of the enzyme. Initially a peroxide reacts with the heme group, yielding Compound I and an alcohol derived from the oxidizing peroxide. Compound I next undergoes an intramolecular reduction by a single electron traveling from Tyr385 along the peptide chain to the proximal heme ligand, His388, and finally to the heme group. Following the binding of arachidonic acid, Tyr385 tyrosyl radical initiates the cyclooxygenase reaction by abstracting the 13-pro(5) hydrogen atom to give an arachidonyl radical, which sequentially reacts with two molecules of oxygen to yield PGG$_2$. In order to characterize PGHS peroxidase active site, we examined various lipid peroxides with purified recombinant ovine PGHS proteins and determined the rate constants. The results have shown that twenty-carbon unsaturated fatty acid hydroperoxides have similar efficiency in peroxidation by PGHS, irrespective of either the location of hydroperoxy group or the number of double bonds. It was also confirmed by the subsequent study with PGHS peroxidase active site mutants.

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Photocatalytic oxidation reaction in removal of NH4-N by using TiO2 (TiO2를 이용한 암모니아성 질소 제거에 관한 광촉매 산화반응)

  • 박상원;김정배
    • Journal of Environmental Science International
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    • v.12 no.10
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    • pp.1071-1077
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    • 2003
  • The aim of this study is, firstly, to find out what kinds of inorganic species are produced in the photocatalytic oxidation of ammonium-nitrogen containing water and, secondly, to seek the influence of anion for the photocatalytic oxidation of ammonium contained compounds. The photoenergy above 3 eV(λ <415 nm) was effectively absorbed by TiO$_2$ and TiO$_2$/polymer was used to be oxidized NH$_4$-N in wastewater to NO$_3$-N. Existing the anion as Cl$\^$-/, the rate of photocatalytic oxidation decreased regardless of other condition. This result showed that the chloride ions reduced the rate of oxidation by scavenging oxidizing radical species as OH$\^$-/ and OCl$\^$-/. Some of the added ion might have blocked the active sites of the catalyst surface, thus deactivated the catalyst.

Preparation and Characterization of Proton Conducting Membranes by Blending PVC-g-PHEA and PVA

  • Koh, Jong-Kwan;Choi, Jin-Kyu;Seo, Jin-Ah;Zeng, Xiaolei;Kim, Jong-Hak
    • Korean Membrane Journal
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    • v.11 no.1
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    • pp.1-7
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    • 2009
  • This work reports the preparation of proton conductive crosslinked polymer electrolyte membranes by blending poly(vinyl chloride)-g-poly(hydroxyl ethyl acrylate) (PVC-g-PHEA) and poly(vinyl alcohol) (PVA). The PHEA chains of the graft copolymer were crosslinked with PVA using sulfosuccinic acid (SA) via the esterification reaction between -OH of polymer matrix and -COOH of SA. The PVC-g-PHEA graft copolymer was synthesized via atom transfer radical polymerization (ATRP) using direct initiation of the secondary chlorines of PVC backbones. Ion exchange capacity (IEC) continuously increased with increasing concentrations of SA, due to the increasing portion of charged groups in the membrane. However, the water uptake increased up to 20.0 wt% of SA concentration above which it decreased monotonically. The membrane exhibited a maximum proton conductivity of 0.026 S/cm at 20.0 wt% of SA concentration, which is presumably due to competitive effect between the increase of ionic sites and the crosslinking reaction.

Thermostable Sites and Catalytic Characterization of Xylanase XYNB of Aspergillus niger SCTCC 400264

  • Li, Xin Ran;Xu, Hui;Xie, Jie;Yi, Qiao Fu;Li, Wei;Qiao, Dai Rong;Cao, Yi;Cao, Yu
    • Journal of Microbiology and Biotechnology
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    • v.24 no.4
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    • pp.483-488
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    • 2014
  • In order to improve the expression of heat-resistant xylanase XYNB from Aspergillus niger SCTCC 400264, XynB has been cloned into Pichia pastoris secretary vector pPIC9K. The XynB production of recombinant P. pastoris was four times that of E. coli, and the $V_{max}$ and specific activity of XynB reached $2,547.7{\mu}mol/mg$ and 4,757 U/mg, respectively. XynB still had 74% residual enzyme activity after 30 min of heat treatment at $80^{\circ}C$. From the van der Waals force analysis of XYNB (ACN89393 and AAS67299), there is one more oxygen radical in AAS67299 in their catalytic site, indicating that the local cavity is much more free, and it is more optimal for substrate binding, affinity reaction, and proton transfer, etc, and eventually increasing enzyme activity. The H-bonds analysis of XYNB indicated that there are two more H-bonds in the 33rd Ser of XYNB (AAS67299) than in the 33rd Ala(ACN89393 ), and two H-bonds between Ser70 and Asp67.