• Journal of the Korean Chemical Society
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• v.41 no.4
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• pp.198-204
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• 1997

The rate constants for the hydrolysis of N-(2,4-dinitrophenyl)benzhydrazonyl bromide and its derivatives were determined by ultraviolet visible spectrophotometry at 20$^{\circ}C$ and a rate equation which could be applied over a wide pH range was obtained. On the basis of rate equations derived and judging from the solvent effect, substituent effect, salt effect, thermodynamic parameter, plausible mechanisms of hydrolysis have been proposed. It may be concluded that the hydrolysis through SN1 mechanism via carbonium ion intermdiate to pH 3.0, and pH 10.0, the hydrolysis proceeds through 1,3-dipolar or SN2 mechanism.

• KSBB Journal
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• v.17 no.6
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• pp.543-548
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• 2002

The enantioselective esterification of racemic ibuprofen catalyzed by a Candida rugosa lipase was studied according to reaction conditions such as a lipase concentration, reaction temperature, alcohol chain length and alcohol concentration. The S-(+)-ibuprofen alkyl esters prepared were converted to S-(+)-ibuprofen by hydrolysis with sulfuric acid as a catalyst. High conversions in the esterifications were obtained at 60$^{\circ}C$ and an equimolar ratio of octanol to ibuprofen. The initial reaction rate of the esterification decreased with increasing octanol concentration. Conversion and initial reaction rate increased with increasing alcohol chain length. Values of enantiomeric excess(ee) according to esterification reaction conditions did not change below 60$^{\circ}C$. On the other hand, values of conversion and ee for the chemical hydrolysis of S-(+)-ibuprofen alkyl esters were independent of alcohol alkyl chain length. Optical resolution of racemic ibuprofen was achieved by lipase catalyzed esterification and chemical hydrolysis. The separation method provided a high yield and enantioselectivity for the production of S-(+)-ibuprofen from racemic ibuprofen.

• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.516-520
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• 2011

Sodium borohydride, $NaBH_4$, shows a number of advantages as hydrogen source for portable proton exchange membrane fuel cells (PEMFCs). The hydrogen yield of sodium borohydride hydrolysis reaction was studied. The effect of temperature, $NaBH_4$ concentration, NaOH concentration and catalyst type on the hydrogen yield from $NaBH_4$ hydrolysis reaction were measured. The catalysts of Co-P/Cu, Co-B/Cu and Co-P-B/Cu were used in this study and there was no different effect of these catalysts on the hydrogen yield from $NaBH_4$. Under the temperature of $60^{\circ}C$, the hydrogen yield decreased as $NaBH_4$ concentration increased due to formation of gel with by-products and reactants. The gel formed during $NaBH_4$ hydrolysis reaction diminished the hydrogen evolution rate and total volume of hydrogen. Addition of NaOH stabilizer enhanced the formation of gel and then decreased the hydrogen yield.

• Applied Biological Chemistry
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• v.48 no.2
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• pp.115-119
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• 2005

The catalytic hydrolysis reactivities of dinuclear nickel (II) complex, ${\mu}-aquapentaaqua[{\mu}-3,6-bis(6'-methyl-2'-pyridyl)pyridazine]chlorodinickel\;(II)$ trichloride trihydrate (APNT) for bis(p-nitrophenyl) phosphate (BNPP) as a DNA model compound were investigated. The dissociation constants of APNT were $pKa_1=7.9$ and $pKa_2=9.6$, respectively. The hydrolysis rate constant of BNPP compound by APNT was showed the rate enhancement of about 370,000 times in the case of none catalyst at pH 7.0 and $50^{\circ}C$. Based on the findings, we proposed the catalytic cycle for the hydrolysis of BNPP by APNT complex. The metal ions of dinuclear nickel (II) complex significantly enhance the transfer rate of phosphoryl group in the catalytic process and the water molecules as nucleophile and proton transfer agent act in different steps.

• Journal of the Korean Ceramic Society
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• v.25 no.5
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• pp.50-50
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• 1988

The controlled Ti(CO2H5)4 hydrolysis reactions for the synthesis of Spherical Monodispersed Titania powders are described. Increasing the concentration of TEOT and the molar ratio of water to TEOT in alcohol solution decrease the reaction time and the particle size. The reaction time is delalyed by increasing the chain length and the number of carbon branches of alcohol as a solvent. The prepared powders with an average diameter of 0.8μ and the spherical monodispersed transfer to Rutile phase at 550℃.

• Korean Chemical Engineering Research
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• v.45 no.6
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• pp.677-679
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• 2007

Nearly monodisperse spherical silica particles, 200~300 nm in diameter, were produced via a dry route for the first time through a two-stage hydrolysis of $SiCl_4$ vapor. In the first stage, the $SiCl_4$ was partially hydrolyzed in a batch reactor at $150^{\circ}C$ to form nearly monodisperse silicon oxychloride particles. In the second stage, the oxychlorides were hydrolyzed further in a tubular reactor to have produced silica with the morphology and size nearly conserved.

• Journal of the Korean Chemical Society
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• v.20 no.1
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• pp.48-55
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• 1976

The rate constants of the derivatives of N-(2,4-dinitrophenyl)-benzimidoyl chloride were determined at various pH and a rate equation which can be applied over wide pH range was obtained. The reaction mechanism of hydrolysis of N-(2,4-dinitrophenyl)-benzimidoyl chloride which has not been studied carefully earlier in acidic and basic solution can be fullly explained by the rate equation obtained. The rate equation reveals that, beow pH 7.00, the hydrolysis of benzimidoyl chloride proceeds through $S_N2$ reaction to form a carbonium ion intermediate.Above pH 8.5, however, the hydrolysis proceeds through the $S_N2$ type reaction which depends on hydroxide ion and imidoyl chloride concentration. At pH 7.0∼8.5, two reactions occur competitively.

• Clean Technology
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• v.12 no.3
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• pp.145-150
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• 2006

Electrolysis of aqueous solution produces hydroxide ions and proton ions for the hydrolysis of reactive organic compounds, and oxidizing agent such as hypochlorite ions for the oxidative decomposition of organic chemicals. Electrolytic decomposition of dying chemicals was tested with our custom made system, and analyzed by HPLC and UV-VIS spectrophotometer. The electrolytic system could decompose dying chemicals with very high reactivity and low cost. Disposal of byproduct and refill of reactant during electrolysis was not necessary. Decomposition time of dying chemicals is compared under similar conditions, and application to water purification is discussed.

• Korean Chemical Engineering Research
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• v.43 no.6
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• pp.715-721
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• 2005

The SMB chromatography is used to obtain high purification of fructooligosaccharides (FOS), the mixture of kestose and nystose. SMB operation condition is usually determined by triangle theory or standing wave design when reactions do not occur within columns during experiment. Some of the reactions in columns may considerably affect experimental results. FOS can be hydrolyzed and converted into glucose and fructose during operation. To include the effect of reaction, the concentrations of each component at steady state after hydrolysis were used in simulation. The obtained simulation values are well matched with experimental results except sucrose. For sucrose, the experimental results were different from expected one due to the existence of an intermediate component. FOS is easily hydrolyzed and converted into glucose and fructose in more acidic condition and at higher temperature. Hydrolysis reaction can be prevented by the pretreatment of separation resin with NaOH as well as operation under lower temperature.

• 한국생물공학회:학술대회논문집
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• 2000.11a
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• pp.447-450
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• 2000

Microorganism, including some bacteria isolated from soil, were found to secrete an extracellular soymilk-clotting enzyme. Using this bacterial enzyme experiments were carried out to optimize the hydrolyzing conditions for the production of soy peptides. The soy peptides produced by hydrolyzing 11S globulin with enzyme treatment at $65^{\circ}C$, pH 6.1, for 1hr were found to have a accessible possibility. The obtained coagulum by enzymatic reaction was very flocculation with fine structural formation. Properties of peptide Y and W of the enzyme hydrolysates at pH 6.1 were superior to that of isoelectric precipitation because these peptides were miscible with water in all proportions.