• Title/Summary/Keyword: condensation reaction

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The Effect of pH on the Condensation Reaction of Benzaldehyde and Semicarbazide (Benzaldehyde와 Semicarbazide의 결합에 미치는 pH치의 영향)

  • 이길상;김인자
    • YAKHAK HOEJI
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    • v.6 no.1
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    • pp.5-7
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    • 1962
  • Like the condensation reaction of general aldehyde, that of benzaldehyde with semicarbazide also depends upon the concentration of carbonium ion that is produced by hydrogen ion. The lower pH value is the facility of the formation of carbonium ion in the condensation reaction, while the reactivity of semicarbazide as a reactant is reduced. In this paper, therefore we want to find out the optimum pH value in the condensation reaction of benzaldehyde with semicarbazide. This optimum pH value was determined by using the simple paper-chromatographic method. According to the result of this experiment, the condensation reaction between benzaldehyde and semicarbazide reacts with its highest point at 3.5pH value. It seems clear that at this point the benzaldehyde acquires the most suitable amount of carbonium ion for the condensation reaction with semicarbazide, and the semicarbazide also has the optimum reactivity.

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Partial Purification and Characterization of ${\beta}$-Ketothiolase from Alcaligenes sp. SH-69

  • Oh, Deok-Hwan;Chung, Chung-Wook;Kim, Jeong-Yoon;Rhee, Young-Ha
    • Journal of Microbiology
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    • v.35 no.4
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    • pp.360-364
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    • 1997
  • A ${\beta}$-ketothiolase was purified 180-fold from the cell extracts of Alcaligenes sp. SH-69 by a series of chromatography on DEAE-Dephadex A-50, Sephacryl S-200, and hydrozyapatitie columns, The optimum pH values of the partially purified enzyme were 7.5 for condensation reaction and 8.3 for thiolysis reaction were estimated to be 0.12mM and $18.7\;{\mu}M$, respectively. The $K_m$ valued for acetoacetyl-CoA and free CoASH in the thiolusis in the condensation reaction was 0.70mM. The condensation reaction of the ${\beta}$-ketothiolase was inhibited even by low concentrations of free CoASH($K_i=30.4{\mu}M$). Pretreatment of the enzyme with NADH and NADPH markedly inhibited the thiolysis reaction of the enzyme. The potent inhibition of the enzyme by sulfhydryl reagents suggests the involvement of cystein residue in the active site.

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Synthesis of Maltosyl-$\beta$-Cyclodextrin through the Reverse Reaction of Pullulanase (Pullulanase의 Reverse Reaction을 이용한 Maltosyl-$\beta$-Cyclodextrin의 합성)

  • 한일근;이용현
    • Microbiology and Biotechnology Letters
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    • v.19 no.5
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    • pp.444-449
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    • 1991
  • Synthesis of maltosyl-$\beta$-cyclodextrin using maltose ($G_2$) and $\beta$-cyclodextrin ($\beta$-CD) as substrates through the reverse reaction of pullulanase was investigated. The optimal conditions for the condensation reaction were as below: mixing ratio of maltose to $\beta$-CD of 12.7, mixed substrate concentration of 70% (w/w, 70 g/100 ml $H_2O$), and amount of pullulanse of 350 units/100 ml. The concentration of synthesized maltosyl-P-CD concentration was reached up to 2.31 g/100 rnl at above reaction conditions, which corresponded the conversion yield of 43% (w/w, g of branched-CD/g of CD). The synthesis of maltosyl-$\alpha >\gamma >\beta$-CD was also attempted, and conversion yield was in the order of a>y>J3-CDs. Condensation reaction between various maltooligosaccharides ($G-1\sim G_6$ showed that maltose was the most effective oligorner for condensation reaction with $\beta$-CD. To increase the conversion yield various alcohols were added into the reaction mixture, amyl alcohol was found to be the most acceptable alcohol for increasement of convesion yield which increased from 43.0 to 83.0% upon addition of same volume of amyl alcohol into the reaction mixture.

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Synthesis of Resol Type Phenol Resins and Their Reaction Properties (Resol형 페놀수지의 합성과 반응특성)

  • Kim, Dong-Kwon;Joe, Ji-Eun;Kim, Jung-Hun;Park, In Jun;Lee, Soo-Bok
    • Applied Chemistry for Engineering
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    • v.16 no.2
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    • pp.288-291
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    • 2005
  • Resol type phenol-formaldehyde (PF) resin was synthesized by addition reaction of formaldehyde (F) and phenol (P). And the PF resin was synthesized by condensation reaction in which water was removed. In this work, we studied the influence of experimental parameters in the addition reaction, such as F/P mole ratio, amount of catalyst, reaction temperature, reaction time, and so on. Also, we studied the influence of molecular weight and viscosity of PE resin as a function of condensation time. As a result, in addition reaction, the reaction time decreased remarkably as the catalyst concentration increased, and the time decreased with increasing reaction temperature at a constant catalyst concentration. Also, in condensation reaction, the viscosity of resol type PF resin increased from 1500 to 9000 cps as a function of condensation time; molecular weight showed from 500 to 1100 g/mol.

Effects of Hydrophilic Surface Treatment on Condensation Heat Transfer at the Outside Wall of Horizontal Tube (수평관 외벽에서 친수성 표면처리가 응축열전달에 미치는 영향)

  • 황규대;박노성;강병하
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.12 no.6
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    • pp.533-540
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    • 2000
  • Condensation heat transfer characteristics have been investigated experimentally when a water vapor is condensed on the outside of a horizontal copper tube in a condenser. This problem is of particular interest in the design of a LiBr-water absorption system. Hydrophilic surface modification was performed to increase the wettability on the copper tube. The optimum hydrophilic treatment condition using acethylene and nitrogen as reaction gas is also studied in detail. The results obtained indicate that the optimum reaction gas ratio of acethylene to nitrogen for hydrophilic surface modification was found to be 7 : 3 for the best condensation heat transfer. In the wide ranges of coolant inlet temperatures, and coolant mass flow rates, both the condensation heat transfer rate and the condensation heat transfer coefficient of a hydrophilic copper tube are increased substantially, compared with those of a conventional copper tube used in a condenser. It is also found that the condensation heat transfer enhancement by the hydrophilic surface modification still emains even after a hundred cycles of wet/dry processes.

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The Significance of Pyrazine Formation in Flavor Generation during the Maillard Reaction

  • Yoo, Seung-Seok
    • Preventive Nutrition and Food Science
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    • v.2 no.4
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    • pp.360-367
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    • 1997
  • The chemistry background of the Maillard reaction focused on pyrazines and factors affecting the reaction products were reviewed. The Maillard reaction, also called a non-enzymatic browning reaction, is quite complex and generates numerous reaction products. In processed foods, it is generally accepted as a key reaction to produce flavor components. Specially, pyrazines possess an important impact character on the roasted foods with other heterocyclic compounds. The Maillard reaction is initiated by condensation between reducing sugar and amino group, and N-glycosylamines are produced via Schiff base with dehydration of water. After the rearrangement of the N-glycosylamines, they follow transformation into deoxyhexosones which are reactive intermediates. Degradation and fragmentation are facilitated by rearranged compounds. By condensation, pyrazine, one of the final Maillard products, is generated as a relatively stable form to provide specific aromas. During the processes of the reaction, chemical or physical environmental parameters affect the formation of the products.

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Studies on the Aromatic Dihydrazines (Ⅱ). Condensation Reaction Between p-Phenylenedihydrazine and Dicarbonyl Compounds (芳香族 디히드라진에 關한 硏究 (第2報). 파라페닐렌디히드라진과 디카르보닐 化合物과의 縮合反應)

  • Lee Woo Young
    • Journal of the Korean Chemical Society
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    • v.20 no.6
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    • pp.500-506
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    • 1976
  • Structures of the products obtained from the condensation reaction between p-phenylenedihydrazine(PPDH) and dicarbonyl compounds were determined, From the reaction with PPDH, acetylacetone produced a cyclic compound, 1,1'-p-phenylene-bis-3, 5-dimetylpyrazole; ethylacetoacetate also formed a cyclic compound, 1,1'-p-phenylene-bis-3-methyl-5-pyrazolone; diacetyl yielded a simple dihydrazone, diacetyl p-phenylenedihydrazone. Condensation products from the other dicarbonyl compounds being of generally unstable, the structure determination was quite difficult.

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Effect of Urea-Formaldehyde Resin Adhesive Viscosity on Plywood Adhesion

  • Hong, Min-Kug;Park, Byung-Dae
    • Journal of the Korean Wood Science and Technology
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    • v.45 no.2
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    • pp.223-231
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    • 2017
  • This work was conducted to investigate on the effect of urea-formaldehyde (UF) resin viscosity on plywood adhesion. The viscosity of UF resin was controlled either by adjusting the condensation reaction during its synthesis to obtain different target viscosities (100, 200 and 300 mPa.s) at two levels of formaldehyde/urea (F/U) mole ratios (1.0 and 1.2) or by adding different amounts (10, 20 and 30%) of wheat flour into the resins for the manufacture of plywood. When the viscosity of UF resin increased by the condensation reaction, the adhesion strength of plywood bonded with UF resin of 1.2 F/U mole ratio consistently increased, while those bonded with the 1.0 F/U mole ratio resin slightly decreased, suggesting a difference in the adhesion in plywood. However, the adhesion strength of plywood decreased as the viscosity increased by adding wheat flour, regardless of F/U mole ratio. The manipulation of UF resin viscosity by adjusting the condensation reaction was much more efficient than by adding wheat flour in improving the adhesion performance of plywood. These results indicated that a way of controlling the viscosity of UF resin adhesives has a great influence to their adhesion in plywood.

Observation of Surface Energy Variations and Condensate Behaviors on Nitrogen Ion Implanted Aluminum Surfaces (질소이온 조사된 알루미늄 표면의 표면에너지 변화 및 증기응축 현상 관찰)

  • Kim, Kiwook;Jeong, Ji Hwan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.29 no.12
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    • pp.621-627
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    • 2017
  • Nitrogen ion with various levels of dose and irradiation energy was irradiated on aluminum surfaces. Contact angle of surface was increased and surface color was changed by nitrogen ion implantation. During steam condensation experiment using nitrogen ion implanted specimen, dropwise condensation initially occurred on specimens. However, condensation mode eventually changed into filmwise condensation. The color of the surface was also changed from yellow-brown to silver-white. This change of surface color and condensation mode were results of hydrolysis reaction between condensate and nitrogen ion implanted on aluminum surfaces.

Synthesis, Characterization and Application of Poly(4-Methyl Vinylpyridinium Hydroxide)/SBA-15 Composite as a Highly Active Heterogeneous Basic Catalyst for the Knoevenagel Reaction

  • Kalbasi, Roozbeh Javad;Kolahdoozan, Majid;Massah, Ahmadreza;Shahabian, Keinaz
    • Bulletin of the Korean Chemical Society
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    • v.31 no.9
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    • pp.2618-2626
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    • 2010
  • In this paper poly (4-methyl vinylpyridinium hydroxide)/SBA-15 composite was prepared as a highly efficient heterogeneous basic catalyst by in situ polymerization method for the first time. It was characterized by XRD, FT-IR, BET, TGA, SEM and back titration using NaOH. This catalyst exhibited the excellent catalytic activities for the Knoevenagel condensation of various aldehydes with ethyl cyanoacetate. Over this catalyst, ${\alpha},{\beta}$-unsaturated carbonyl compounds were obtained in the reasonable yield at $95^{\circ}C$ in 10 - 30 min in $H_2O$ as a solvent with a 100% selectivity to the condensation products. Catalyst could be easily recycled after the reaction and it could be reused without the significant loss of activity/selectivity performance. No by-product formation, high yields, short reaction times, mild reaction conditions and operational simplicity with reusability of the catalyst were the salient features of the present synthetic protocol. Presence of $H_2O$ as a solvent was also recognized as a "green method".