• Bulletin of the Korean Chemical Society
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• v.35 no.9
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• pp.2673-2678
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• 2014

The detailed mechanisms of the efficient $\small{L}$-proline and pyrrolidine catalyzed transamidation of acetamide with benzylamine have been investigated using density functional theory (DFT) calculations. Our calculated results show: (1) the mechanisms of two catalytic cycle reactions are similar. However, the rate-determining steps of their reactions are different for the whole catalytic process. One is the intramolecular nucleophilic addition reaction of 1-COM, the other is hydrolysis reaction of 2-C. (2) COOH group of $\small{L}$-proline is essential for efficient transamidation. The computational results are in good agreement with the experiment finding and mechanism resported by Rao et al. for $\small{L}$-proline-catalyzed synthesis of amidesin good to excellent yields.

• Clean Technology
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• v.28 no.3
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• pp.232-237
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• 2022

Biorefineries, in which renewable resources are utilized, are an eco-friendly alternative based on biomass feedstocks. Alginic acid, a major component of brown algae, which is a type of marine biomass, is widely used in various industries and can be converted into value-added chemicals such as sugars, sugar alcohols, furans, and organic acids via catalytic hydrothermal decomposition under certain conditions. In this study, ruthenium-supported activated carbon and magnesium oxide were mixed and applied to the depolymerization of alginic acid in a batch reactor. The addition of magnesium oxide as a basic promoter had a strong influence on product distribution. In this heterogeneous catalytic system, the separation and purification processes are also simplified. After the reaction, low molecular weight alcohols and organic acids with 5 or fewer carbons were produced. Specifically, under the optimal reaction conditions of 30 mL of 1 wt% alginic acid aqueous solution, 100 mg of ruthenium-supported activated carbon, 100 mg of magnesium oxide, 210 ℃ of reaction temperature, and 1 h of reaction time, total carbon yields of 29.8% for alcohols and 43.8% for a liquid product were obtained. Hence, it is suggested that this catalytic system results in the enhanced hydrogenolysis of alginic acid to value-added chemicals.

• Applied Chemistry for Engineering
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• v.8 no.6
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• pp.920-926
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• 1997

The catalytic glycolysis process is the method of chemical recycling where the polyol and carbamate compounds recovered by transesterification reaction are reused to produce new polyurethane foams. In this work, ethylene glycol, diethylene glycol, and 1,4-butanediol were used to decompose polyurethane foams and various metallic acetates were provided as catalysts. The catalytic glycolsis of polyurethane foams was taken place in the reaction temperature of $180{\sim}200^{\circ}C$. The reaction rates of catalytic glycolysis reaction were indicated by the viscosity of the reaction products at different reaction times. IR and GPC analysis showed the types and the molecular weight distributions of the products. The catalytic glycolysis was profitable for using ethyleneglycol at high temperature. The activities of the catalysts are suitable for K, Na, Tl acetate, and the products are composed of comparatively high-contained amine compounds and carbamate compounds. In the case of Sr acetate and Quinoline, the reaction rate was somewhat low. However, the content of polyol was high and the content of the side-products was low. The foams which were prepared by blending up to 20wt% of recovered polyol with virgin polyols showed better physical properties in tensile strength, hardness, tear strength, and compressive strength compared to those of polyurethane foams from virgin polyol.

• Bulletin of the Korean Chemical Society
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• v.22 no.3
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• pp.263-266
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• 2001

Isopropylation of phenol with 2-propanol has been carried out over Na-exchanged ZSM-5 zeolites to determine the effect of catalyst acidity on phenol conversion and product selectivity. The acid type and strength of the catalyst such as Lewis, weak and strong Bronsted acid sites are measured by pyridine adsorbed XPS and the catalytic properties are interpreted in terms of the acid properties. The active site and mechanism for the reaction are suggested based on evidence of study from the reactant adsorbed FT-IR.

• Journal of Microbiology and Biotechnology
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• v.8 no.5
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• pp.471-477
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• 1998

Taq DNA polymerase from Thermus aquaticus is very useful in the polymerase chain reaction. Taq DNA polymerase is classified in the pol I family, represented by E. coli DNA polymerase I. The three-dimensional structural alignment of 3'-5'exonuclease domains from the pol I family DNA polymerases explains why Taq DNA polymerase does not carry out proofreading in polymerase chain reactions. Three sequence motifs, Exo I, II, and III, must exist to carry out 3'-5'exonuclease activity for proof- reading by a 3'-5'exonuclease reaction, but these are abolished in Taq DNA polymerase. The key catalytic module in 3'-5'exonuclease is two metal ions chelated by four active-site carboxylic amino acids. Taq DNA polymerase was mutagenized to construct the catalytic module in the active site. The circular dichroism technique supported the formation of the catalytic module, and the radioactive assay showed that the 3'-5'exonuclease activity doubled in the mutant Taq DNA polymerase.

• Korean Chemical Engineering Research
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• v.56 no.3
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• pp.416-420
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• 2018

A comprehensive kinetic study has been conducted on dimethyl carbonate synthesis by transesterification reaction of ethylene carbonate with methanol. An alkali base metal (KOH) was used as catalyst in the synthesis of DMC, and its catalytic ability was investigated in terms of kinetics. The experiment was performed in a batch reactor at atmospheric pressure. The reaction orders, the activation energy and the rate constants were determined for both forward and backward reactions. The reaction order for forward and backward reactions was 0.87 and 2.15, and the activation energy was 12.73 and 29.28 kJ/mol, respectively. Using the general factor analysis in the design of experiments, we analyzed the main effects and interactions according to the MeOH/EC, reaction temperature and KOH concentration. DMC yield with various reaction conditions was presented for all ranges using surface and contour plot. Furthermore, the optimal conditions for DMC yield were determined using response surface method.

• Bulletin of the Korean Chemical Society
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• v.32 no.4
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• pp.1195-1200
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• 2011

The catalytic enantioselective Mannich-type reaction promoted by chiral binaphthyl-modified bifunctional organocatalysts is described. The treatment of ${\alpha}$-fluoro-${\beta}$-ketoesters with N-Boc imines under mild reaction conditions afforded the corresponding ${\beta}$-aminated ${\alpha}$-fluoro-${\beta}$-ketoesters with excellent enantioselectivities (up to 98% ee).

• Bulletin of the Korean Chemical Society
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• v.8 no.4
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• pp.329-332
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• 1987

The reaction of (E)-1-alkenyl-1,3,2-benzodioxaboroles with a variety of allylic phenoxides in the presence of a catalytic amount of Pd$(PPh_3)_4$ is described. The reaction affords a general and simple procedure for the preparation of 1,4-alkadienes from alkynes via hydroboration.

• Korean Chemical Engineering Research
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• v.59 no.4
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• pp.481-486
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• 2021

In a hypersonic vehicle to solve the heat problem generated during flight, a cooling technology is being developed which uses the endothermic effect that appears during the decomposition reaction of the mounted fuel. In this study, the decomposition reaction of n-dodecane fuel was performed using HZSM-5 as a catalyst, and the catalyst was coated on metal foam to maximize the endothermic effect of the catalytic decomposition reaction and suppress coke formation. The reactor was a stainless steel flow reactor with a outer diameter of 1.27 cm, and the reaction temperature was 550 ℃, the reaction pressure was 4 MPa, and the flow rate was 12 ml per minute. As a result of the catalytic decomposition reaction using a catalyst coated with HZSM-5 on the metal foam, the heat sink was 2887 kJ/kg as a maximum, the gas phase conversion rate was 34%, and the amount of coke produced on the metal foam decreased by about 56% as the catalyst was coated compared to the uncoated catalyst.

• Bulletin of the Korean Chemical Society
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• v.17 no.11
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• pp.1040-1044
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• 1996

The catalytic dehydrocoupling of bis(1-sila-3-butyl)benzene, 1 by Cp2ZrCl2/Red-Al and Cp2ZrCl2/n-BuLi combination catalysts yielded a mixture of oily and solid polymers. While the catalytic dehydrocoupling of 2-phenyl-l,3-disilapropane, 2 by Cp2ZrCl2/n-BuLi combination catalyst produced a mixture of oily and solid polymers, the catalytic redistribution/dehydrocoupling of 2 by Cp2ZrCl2/Red-Al combination catalyst gave oily polymer. The dehydrocoupling of 1 and 2, unless the prior silane redistribution occurs, seems to initially produce a low-molecular-weight polymer, which then undergoes an extensive cross-linking reaction of backbone Si-H bonds, leading to an insoluble polymer.