• Bulletin of the Korean Chemical Society
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• 제30권1호
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• pp.29-30
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• 2009

• Bulletin of the Korean Chemical Society
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• 제24권3호
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• pp.306-310
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• 2003

Hydrolysis reactions of S-phenyl-S-vinyl-N-p-tosylsulfilimine (VSI) and its derivatives at various pH have been investigated kinetically. The hydrolysis reactions produced phenylvinylsulfoxide and p-toluene sulfonamide as the products. The reactions are first order and Hammett ρ values for pH 1.0, 6.0, and 11.0 are 0.82, 0.45, and 0.57, respectively. This reaction is not catalyzed by general base. The plot of k vs pH shows that there are three different regions of the rate constants $(k_t)$ in the profile.; At pH < 2 and pH > 10, the rate constants are directly proportional to the concentrations of hydronium and hydroxide ion catalyzed reactions, respectively. The rate constant remains nearly the same at 2 < pH < 10. On the bases of these results, the plausible hydrolysis mechanism and a rate equation have been proposed: At pH < 2.0, the reaction proceeds via the addition of water molecule to sulfur after protonation at the nitrogen atom of the sulfilimine, whereas at pH > 10.0, the reaction proceeds by the addition of hydroxide ion to sulfur directly. In the range of pH 2.0-10.0, the addition of water to sulfur of sulfilimine appears to be the rate controlling step.

• Journal of Forest and Environmental Science
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• 제31권1호
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• pp.1-6
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• 2015

Microwave assisted biodiesel production from crude Pongamia pinnata oil using homogeneous base catalyst (KOH) was unsuccessful because of considerable soap formation. Therefore, a two step process of biodiesel production from high free fatty acid (FFA) oil was investigated. In first step, crude P. pinnata oil was acid catalyzed using $H_2SO_4$ and acid value of oil was reduced to less than 4 mg KOH/g. Effect of sulfuric acid concentration, alcohol-oil molar ratio and microwave irradiation time on acid value of oil was studied. Result suggested that 1.5% $H_2SO_4$ (w/w), 6:1 methanol oil molar ratio and 3 min microwave irradiation time was sufficient to reduce the acid value of oil from 12 and 22 mg KOH/g to 2.9 and 3.9 mg/KOH/g, respectively. Oil obtained after pretreatment was subsequently used for microwave assisted alkali catalyzed transesterification. A higher biodiesel yield (99.0%) was achieved by adopting two step processes. Microwave energy efficiency during alkali catalyzed transesterification was also investigated. The results suggested a significant energy saving because of reduced reaction time under microwave heating.

• Bulletin of the Korean Chemical Society
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• 제31권3호
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• pp.582-587
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• 2010

A rhodium-catalyzed reductive cleavage reaction of carbon-cyano bonds is developed using hydrosilane as a mild reducing agent. A wide range of nitriles, including aryl, benzyl, and $\beta$-hydrogen containing alkyl cyanides are applicable to this decyanation reaction. The method is also applicable to organic synthesis, in which benzyl cyanide is used as a benzyl anion equivalent and a cyano group functions as a removable ortho-directing group.

• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 2000년도 춘계학술대회
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• pp.8-9
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• 2000

Despite the advances made in the past few decades in cancer chemotherapy, many conventional anticancer drugs display relatively poor selectivity for cancer cells. The nonselectivity of anticancer drugs and the development of anticancer drug resistance have been recognized as serious limitations in their clinical usefulness. Therefore, a major challenge in cancer chemotherapy is the development of new anticancer agents with improved selectivity for tumor cells as well as the prevention of the host cell resistance, both of which result in the improvement of therapeutic effect against cancer cells. Cyclophosphamide (CP), a widely used anticancer agent, is a prodrug that is activated by hepatic microsomal mixed-function oxidase (MFO) catalyzed C$_4$- hydroxylation. The resulting 4-hydroxycyclophosphamide (4-OH-CP) is converted to the ring-opened tautomer to aldophosphamide (Aldo) which subsequently undergoes a base- catalyzed ${\beta}$-elimination to generate cytotoxic phosphoramide mustard (PDA) and acrolein. The cytotoxic activity of CP is attributed to the aziridinium ion species derived from PDA that cross-links interstrand DNA.

• 폴리머
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• 제24권1호
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• pp.124-127
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• 2000

Poly(isobutylene oxide)의 물리적 성질을 개선하기 위하여 isobutylene oxide와 cyclohexene oxide의 공중합체가 triisobutylaluminum을 촉매로 하여 합성되었다. 분자량은 diethylzinc를 촉매로 하여 만든 poly(isobutylene oxide)보다 낮았다. 유리전이온도는 두 개의 단일중합체 사이에 일정하게 분포되었다. Vinyl cyclohexene oxide와의 공중합체는 현저한 열안정성을 보여주었다. 폴리올이나 윤활제로 응용 가능한 올리고머가 제조되었다. 산촉매하에서는 복잡한 생성물 분포를 보여 주었으나 염기 촉매하에서는 오량체 및 육량체가 주인 생성물 분포를 보여주었다.

• 대한화학회지
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• 제36권3호
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• pp.446-452
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• 1992

80% acetonitrile-20% water(v/v) 용액에서 piperidine에 의한 aryl phenylacetate류의 가수분해 반응 속도를 측정하였다. 이탈되는 phnol의 치환기가 전자받개인 경우, 가수분해는 일반 염기촉매로 진행되며 $30^{\circ}C$에서 Hammett $\rho_{LG}$값은 5.28, Bronsted $\beta$값은 -2.72이었다. 이와 같이 매우 큰 Hammett 및 Bronsted 값은 이 반응이 $E1_{C}B$ 메카니즘으로 가수분해됨을 나타낸다. 한편, 전자주개 치환기의 경우는 특수 염기촉매에 의해 가수분해되며 $B_{AC}2 메카니즘이 우세하게 나타났다. Phenylacetic acid ester의 $pK_{SH}를 구하였으며, piperidine에 의한 ester 반응의 가수분해 속도 상수 $k_1$, $k_{-1)$, $k_2$도 계산하였다.

• 한국세라믹학회지
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• 제37권6호
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• pp.517-523
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• 2000

Effect of catalysts, which was catalyzed by acid(HCl and HNO3) and base(NH4OH), on characteristics of the mullite powders prepared by sol-gel methdo wa sinvestigated by XRD, TGA, SEm AND BET. As a result, weight loss as a function of catalysts was in order of HCl=32.6%>HNO3=25.44%>Non=24.0%>NH4OH=22.5%. The mullite powder dried at 100$^{\circ}C$ appeared spherical shape in acid catalyst and different shape in base catalyst, but sintering powder at 1400$^{\circ}C$ appeared very fine particle of 0.05∼0.1$\mu\textrm{m}$ regardless of catalysts. In all cae, the pore quantity, which was capable to adsoprtion, was decreased with increasing temperature. In base catalyst, no change of special surface area in mullite appeared.

• Bulletin of the Korean Chemical Society
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• 제30권7호
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• pp.1583-1587
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• 2009

The four dentate $N_2O_2$ Schiff base ligand of bis(2-hydroxyacetophenone)-1,2-propanediimine (BHAPN) and its manganese (III) complex were synthesized and identified by microanalysis, spectral data ($^1H$ NMR, MS, FT-IR and UV-Visible) and molar conductivity measurement. The mild and efficient homogeneous oxidative decarboxylation of some carboxylic acids by catalytic amount of this manganese (III) complex, using tetrabutylamonium periodate as a mild oxidant in chloroform at room temperature is reported. The catalyst used in this study showed good activity for the decarboxylation of the titled compounds.

• Applied Biological Chemistry
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• 제38권5호
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• pp.455-462
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• 1995

새로운 6종의 제초성, N-(2,6-dimethoxypyrimidin-2-yl)aminocarbonyl-2-치환(Z)-6-(1-hyd roxy-2-fluoroethyl)benzenesulfonamide 유도체(S)를 합성하여 $45^{\circ}C$의 15%(v/v) acetonitrile 수용액속에서 일어나는 가수분해 반응상수를 측정하고 pH-효과, 용매효과, ortho-치환기 효과, 열 역학적 활성화 파라미터(${\Delta}H^{\neq}$및${\Delta}S^{\neq}$) 등의 반응 속도론적인 자료들과 pKa상수(4.80) 및 가수분해 반응 생성물(2-(1-hydroxy-2-fluoroethyl)benzenesulfonamide 및 4,6-dimethoxyaminopyrimidine) 분석 등의 비 반응 속도론적 결과로부터 반응속도식을 유도하고 반응메카니즘을 제안하였다. pH 8.0 이하에서는 일반 산-촉매반응($A-S_E2$)과 특정 산-촉매 반응으로 conjugate acid ($SH^+$)와 사면체 중간체(I)를 경유하는 A-2형(또는 $A_{AC}2$형)반응 그리고 pH 9.0 이상에서는 물 분자가 일반염기(B)로 작용하여 conjugate base (CB)를 경유하는 $(E_1)_{anion}$ 반응으로 진행되는 가수분해 반응 메카니즘을 검토하였으며 pH $7.0{\sim}9.0$사이의 용액중에서는 이들 두 반응이 경쟁적으로 일어남을 알았다.