• Journal of the Korean Chemical Society
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• v.36 no.3
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• pp.446-452
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• 1992

The rates of hydrolysis of aryl phenylacetates have been measured in the presence of piperidine in 80% acetonitrile-20% water(v/v). For the electron withdrawing substituents of leaving group, the hydrolysis is catalyzed by a general base and the Hammett $\rho_{LG}$ and Bronsted value $\beta$ are 5.28 and -2.72 at $30^{\circ}C$, respectively. These high senstivities of Hammett and Bronsted values are $E1_{C}B$ mechanism. But in the electron donating ones, the hydrolysis is catalyzed by a specific base and $B_{AC}2 mechanism is predominated. $pK_{SH}'s of phenylacetic acid ester and rate constants of hydrolysis $k_1$, $k_{-1)$, $k_2$ were calculated.

• Proceedings of the PSK Conference
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• 2003.04a
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• pp.244.2-244.2
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• 2003

For the development of new synthetic method for unnatural amino acid esters, alkyl ${\alpha}$-anilinophenylacetates were synthesized through base-catalyzed hydrolysis of 1,5-diphenylhydantoins in methanol and O-alkylation of sodium ${\alpha}$-anilinophenylacetate with alkyl halides in DMF. Even though hydrolysis of hydantoin ring was undertaken under about 30-40$^{\circ}C$ in methanol, the hydantoic acid sodium salt was continuously converted to the sodium ${\alpha}$-anilinophenylacetate. (omitted)

• Journal of the Korean Chemical Society
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• v.35 no.2
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• pp.184-186
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• 1991

• Journal of the Korean Chemical Society
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• v.35 no.6
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• pp.750-752
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• 1991

• Journal of the Korean Chemical Society
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• v.28 no.6
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• pp.436-438
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• 1984

• 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.

• Macromolecular Research
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• v.12 no.4
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• pp.359-366
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• 2004

The polysaccharide, (1\longrightarrow5)-$\alpha$-D-ribofuranan, was synthesized by a cationic ring-opening polymerization of 1,4-anhydro-2,3-di-O-benzyl-$\alpha$-D-ribopyranose with the aid of boron trifluoride etherate and subsequent debenzylation. This polysaccharide catalyzed the hydrolysis of ethyl p-nitrophenyl phosphate, uridylyl(3'\longrightarrow5')uridine ammonium salt, and 4-tert-butylcatechol cyclic phosphate N-methyl pyridinium. The polymer also catalyzed the cleavage of nucleic acids (DNA and RNA). The hydrolysis of ethyl p-nitrophenyl phosphate in the presence of the polymer was accelerated by 1.5 ${\times}$ 10$^3$ times relative to the uncatalyzed reaction. The catalytic activity was attributable to the vic-cis-diols of the riboses being located inside the active center that is formed by polymer chain folding; these diols form hydrogen bonds with two phosphoryl oxygen atoms of the phosphates so as to activate the phosphorus atoms to be attacked by nucleophile ($H_2O$).

• YAKHAK HOEJI
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• v.34 no.6
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• pp.415-421
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• 1990

The effects of temperature, pH, light and concentration on the degradation of trimebutine maleate in aqueous solution were investigated on the basis of accelerated stability analysis, and the stabilization of the solution was attempted by addition of several additives. The decomposition of trimebutine maleate in solution followed first-order reaction the was not only accelerated by temperature elevation but also the lower the concentratin the more speeded up the reaction. The decomposition mechanism of trimebtine could be confirmed by hydrolysis of ester bond in the structure. It was assumed trimebutine maleate is so photosensitive that the solution of the drug underwent accelerated decomposition under UV rays. What is more, the degradation of trimebutine solution was supposed to catalyzed by specific acid-base catalysis considered the pH dependence for the hydrolysis of ester, and the solution was most stable over the range of pH 2-2.8 in solution. The additives, citric acid, asparitc acid and glutamic acid, inhibited considerably the decomposition of the drug solution, and these additives might be used as stabilizers in trimebutine maleate solution.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.511-511
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• 2009

Lignocellulosic biomass is the most abundant organic material on earth and also promising raw material for bioenergy production. Agricultural residues in the process of bio-oil extraction, is an abundant and low-cost lignocellulosic material. The technology for conversion of lignocellulosic biomass resources to fuels and chemicals, such as ethanol, has been under development for decades. One of the well-studied technologies that are currently being commercialized is to use a dilute acid-catalyzed pretreatment followed by enzymatic hydrolysis and fermentation to produce ethanol. In this work, the dilute-acid hydrolysis of agricultural residues was optimized through the utilization of statistical experimental design. Evaluation criteria for optimization of the pretreatment conditions were based on high xylose recovery and low inhibitor contents in the hydrolyzates. The purpose of this study was to gain a more accurate understanding of the quantities of acid required for effective hydrolysis and the reactivity trade-offs with reaction time and temperature that will enable overall process optimization.

• Korean Chemical Engineering Research
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• v.53 no.4
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• pp.478-481
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• 2015

In this study, the hydrolysis of green macro-algae Enteromorpha intestinalis using solid acid catalyst was conducted to obtain total reducing sugar. The hydrolysis was optimized with four reaction parameters of liquid-to-solid (L/S) ratio, catalyst amount, reaction temperature, and reaction time. As a optimized result, the highest TRS of 7.74 g/L was obtained under condition of 7.5 L/S ratio, $140^{\circ}C$, 15% catalyst amount and 2 hr. By the way, at this condition, only 0.13 g/L 5-HMF was detected. The solid acid-catalyzed hydrolysis of marine resources had the potential in the field of bioenergy.