• 제목/요약/키워드: solvent-free media

검색결과 14건 처리시간 0.023초

Solvent-free 조건하에서 H3PMo12O40 촉매에 의한 Z-Aldoximes의 (Regioselective Synthesis of Z-Aldoximes Catalyzed By H3PMo12O40 under Solvent-Free Conditions)

  • Eshghi, Hossein;Alizadeh, Mohammad Hasan;Davamdar, Ehsan
    • 대한화학회지
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    • 제52권1호
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    • pp.52-56
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    • 2008
  • 제법을 위한 쉽고 효과적인 이 방법은 solvent-free하에서 H3PMo12O40 촉매를 사용해서 개선되었다. 이 방법의 큰 이점은 조작의 간편성, 더 작은 촉매량, 선택성, 온화한 반응조건,짧은 반응 시간 그리고 높은 수율이다. 재생된 촉매는 어떤 정제도 없이 다시 사용되어질 수 있다.

On-line Conversion Estimation for Solvent-free Enzymatic Esterification System with Water Activity Control

  • Lee, Sun-Bok;Keehoon Won
    • Biotechnology and Bioprocess Engineering:BBE
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    • 제7권2호
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    • pp.76-84
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    • 2002
  • On-line conversion estimation of enzymatic esterification reactions in solvent-free media was investigated. In principle, conversion to ester can be determined from the amount of water produced by the reaction, because water is formed as a by-product in a stoichiometric manner. In this study, we estimated the water production rate only from some measurements of relative humidity and water balances without using any analytical methods. In order to test the performance of the on-line conversion estimation, the lipase-catalyzed esterification of n-capric acid and n-decal alcohol in solvent-free media was performed whilst controlling water activity at various values. The reaction conversions estimated on-line were similar to those determined by offline gas chromatographic analysis. However, when the water activity was controlled at higher values, discrepancies between the estimated conversion values and the measured values became significant. The deviation was found to be due to the inaccurate measurement of the water content in the reaction medium during the initial stages of the reaction. Using a digital filter, we were able to improve the accuracy of the on-line conversion estimation method considerably. Despite the simplicity of this method, the on-line estimated conversions were in good agreement with the off-line measured values.

Wet SiO2 As a Suitable Media for Fast and Efficient Reduction of Carbonyl Compounds with NaBH3CN under Solvent-Free and Acid-Free Conditions

  • Kouhkan, Mehri;Zeynizadeh, Behzad
    • Bulletin of the Korean Chemical Society
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    • 제31권10호
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    • pp.2961-2966
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    • 2010
  • Reduction of carbonyl compounds such as aldehydes, ketones, $\alpha,\beta$-unsaturated enals and enones, $\alpha$-diketones and acyloins was carried out readily with $NaBH_3CN$ in the presence of wet $SiO_2$ as a neutral media. The reactions were performed at solvent-free conditions in oil bath (70 - $80^{\circ}C$) or under microwave irradiation (240 W) to give the product alcohols in high to excellent yields. Regioselective 1,2-reduction of conjugated carbonyl compounds took place in a perfect selectivity without any side product formation.

Montmorillonite K-10 Clay as an Efficient Reusable Heterogeneous Catalyst for the Solvent-Free Microwave Mediated Synthesis of 5-Substituted 1H-Tetrazoles

  • Marvi, Omid;Alizadeh, Abdolhamid;Zarrabi, Saeid
    • Bulletin of the Korean Chemical Society
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    • 제32권11호
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    • pp.4001-4004
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    • 2011
  • Various 5-substituted 1H-tetrazole derivatives were synthesized in a simple and environmentally benign method from the reaction of aryl and benzyl nitriles with sodium azide in solvent-free media using montmorillonite K-10 clay as solid recyclable heterogeneous acidic catalyst and microwave irradiation in good yields and short reaction times.

NaHSO4·SiO2 촉매를 이용한 Knoevenagel 축합을 거친α,β의 불포화산, α-Cyanoacrylonitriles와 α-Cyanoacrylates의 합성을 위한 무수조건하의 반응 절차 (Dry Media Reaction Procedure for Synthesis of α,β-Unsaturated Acids, α-Cyanoacrylonitriles and α-Cyanoacrylates via Knoevenagel Condensation Using NaHSO4·SiO2 Catalyst)

  • Gopalakrishnan, M.;Sureshkumar, P.;Kanagarajan, V.;Thanusu, J.;Thirunavukkarasu, S.
    • 대한화학회지
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    • 제51권4호
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    • pp.346-351
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    • 2007
  • NaHSO4·SiO2를 사용하는 solvent-free 조건하에서 E-geometry를 가진 α,β의 불포화산, α-Cyanoacrylonitriles 와 α-Cyanoacrylates의 효율적인 입체선택적 반응을 수행하였다.

Electrolyte Effect on the Particle Characteristics Prepared by Soap-Free Emulsion Polymerization

  • Han, Seung-Tak;Lee, Kang-Seok;Shim, Sang-Eun;Saikia, Prakash J.;Choe, Soon-Ja;Cheong, In-Woo
    • Macromolecular Research
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    • 제15권5호
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    • pp.403-411
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    • 2007
  • Monodisperse micron-sized polystyrene (PS) spheres were successfully obtained using a single stage soap-free emulsion method in aqueous media mixed with ethanol (co-solvent) containing NaCI as the electrolyte. The optimum conditions for preparing the monodisperse PS microspheres, using soap-free emulsion polymerization in a water/ethanol mixture with an electrolyte, were studied. The presence of the co-solvent and electrolyte controlled the particle dispersion stability during the polymerization. The microspheres formed using PS, with a weight-average diameter of $2.6{\mu}m$, coefficient of variation of 5.3% and zeta potential of -15.1 eV, were successfully obtained in the presence of 0.1 wt% NaCI, 10 wt% monomer, 0.1 wt% initiator and 95/5 (g/g) of a water/ethanol mixture reacted at $70^{\circ}C$ for 24 h.

긴사슬 알킬 우로칸에스테르의 합성 및 유기물질에서의 가용성 (Synthesis of Long Chain Alkyl Urocanate and Solubilization in Organic Solvent)

  • 노윤찬;정환경;남기대;이진희
    • 한국응용과학기술학회지
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    • 제10권1호
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    • pp.83-91
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    • 1993
  • The syntheses of urocanic acid esters was optimized, starting from p-toluenesulfonic acid salt of this acid and long chain fatty alcohols in the organic solvent and extracting water from it by means of azeotropic Compound. The salts of these urocanic acid esters showed amphoteric properties, but their micellization enhances their rate of hydrolysis leading to the free amine. Nevertheless the long chain gives to the esters themselves an amphoteric character allowing their solubilization in micellar media and in microemulsions the result, yield could enhanced.

Preparation of Substained-Release Microspheres of Phenylpropanolamine HCI and Their Release Characteristics

  • Kim, Chong-Kook;Lee, Kyung-Mi;Hwang, Sung-Joo;Yoon, Yong-Sang
    • Archives of Pharmacal Research
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    • 제13권4호
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    • pp.293-297
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    • 1990
  • Sustained release microspheres containing phenylpropanolamine HCI (PPA) were prepared with acrylic polymer (Eudragit RL/RS) sand hydroxypropylmethylcellulose phthalate (HPMCP) using a emulsion-solvent evaporation method. Magnesium strate was used a smoothing agent for preparation of microspheres. The microspheres obtained were very spherical and free-flowing particles. Scanning electron microscopy showed that microspheres have a smooth surface and a sponage-like internal structure. The dissolution rate of PPA from the microspheres was dependent on the pH of dissolution media. PPA showed faster relase in hP 1. 2 solution than in pH 7.4 solution due to the solubility of PPA. Therefore we prepared new microspheres containing 5% (w/v) HPMCP in order to control the release of PPA. The release rate of PPA from these new microspheres was similar in pH 1.2 and pH 7.4 solution.

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Effect of microwave irradiation on lipase-catalyzed reactions in ionic liquids

  • An, Gwangmin;Kim, Young Min;Koo, Yoon-Mo;Ha, Sung Ho
    • 분석과학
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    • 제30권3호
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    • pp.138-145
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    • 2017
  • Microwave-assisted organic synthesis has gained a remarkable interest over the past years because of its advantages - (i) rapid energy transfer and superheating, (ii) higher yield and rapid reaction, (iii) cleaner reactions. Ionic liquids are well known for their unique properties such as negligible vapor pressure and high thermal stability. With these properties, ionic liquids have gained increasing attention as green, multi-use reaction media. Recently, ionic liquids have been applied as reaction media for biocatalysis. Lipase-catalyzed reactions in ionic liquids provide high activity and yield compared to conventional organic solvents or solvent free system. Since polar molecules are generally good absorbent to microwave radiation, ionic liquids were investigated as reaction media to improve activity and productivity. In this study, therefore, the effect of microwave irradiation in ionic liquids was investigated on lipase catalyzed reactions such as benzyl acetate synthesis and caffeic acid phenethyl ester synthesis. Comparing to conventional heating, microwave heating showed almost the same final conversion but increased initial reaction rate (3.03 mM/min) compared to 2.11 mM/min in conventional heating at $50^{\circ}C$.

토코페롤을 함유하는 생분해성 폴리($\varepsilon$-카프로락톤) 마이크로캡슐의 제조 및 방출 특성 (Preparation and Release Characterization of Biodegradable Poly($\varepsilon$-caprolactone) Microcapsules Containing Tocopherol)

  • 박수진;김기석;민병각;홍성권
    • 폴리머
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    • 제28권2호
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    • pp.103-110
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    • 2004
  • 토코페롤을 함유하는 폴리($\varepsilon$-카프로락톤)(PCL) 마이크로캡슐은 액중건조법에 의하여 제조하였고, 제조 조건에 따른 마이크로캡슐의 특성과 PCL 필름을 사용하여 PCL의 분해거동을 측정하였다 제조된 마이크로캡슐의 크기 및 형태와 구조적 특성은 각각 SEM과 XRD를 이용하여 관찰하였다. 또한, 접촉각 측정을 통하여 심물질의 농도에 따른 마이크로캡슐의 표면자유에너지를 측정하였다. 실험결과, 마이크로캡슐은 유화제로 폴리(비닐 알코올)을 사용한 경우 안정된 구형의 마이크로캡슐이 형성되었고, 마이크로캡슐의 표면자유에너지와 PCL의 결정성은 감소하고, PCL 필름은 악 21일 후 분해가 시작되었다. 토코페롤의 방출특성은 UV/vis.에 의하여 측정하였으며, 마이크로캡슐의 방출속도는 교반속도의 증가와 함께 증가하였다. 이는 교반속도의 증가와 함께 감소된 마이크로캡슐 입자 크기에 의한 방출용액과 마이크로캡슐 사이의 계면의 증가에 의한 것으로 판단된다.