• Bulletin of the Korean Chemical Society
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• v.20 no.6
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• pp.643-647
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• 1999

Hydropalladium carboxylates, formed from π-allylpalladium chloride dimer plus carboxylic acids, have been shown to catalyze cyclization of structurally diverse enediynes to form the corresponding six- or five-membered rings depending upon the reaction conditions. Some enediynes having an Oxygen linker in an appropriate position under the similar condition yielded the corresponding cyclopropanation products in highly stereoselective manner. A study using deuterated formic acid has proven that the alkylpalladium intermediates formed in our conditions were reduced by the pendant formate ligand. The dienediyne 10 yielded only the tricyclic product 12 in 67% yield, although it was expected to frrm the cyclic product 11. All these cyclizations seemed to occur via the corresponding alkylpalladium intermediates I. which could proceed to the corresponding cyclic products depending on the reaction conditions and the substrates. The study using ceuterated formic acid could provide an important information to understand the present cyclization mechanism. Overall the present study could play an important role in developing new synthetic methodologies for constructing complex polycyclic compounds.

• YAKHAK HOEJI
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• v.47 no.1
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• pp.5-9
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• 2003

Synthetic aluminum silicate was prepared by reacting aluminum sulfate solution with Sodium silicate solution in this study. The optimum synthesis conditions based on the yield of the product were established by applying Box-Wilson experimental design. The results were found to be as follows; Reactant temperature : 50∼72$^{\circ}C$, Concentration of two reactants : 10∼17.6％, Mole ratio of two reactants, [Sod. silicate]/[Al. sulfate) : 4.6∼5.0, Temperature of washing water : 25∼4$0^{\circ}C$, and Drying temperature of product : 50∼$65^{\circ}C$. The physical and chemical properties of synthetic aluminum silicate as medicine were investigated by means of chemical analysis, adsorption test and acid consuming capacity measurements.

• Korea Trade Review
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• v.44 no.1
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• pp.237-251
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• 2019

This paper seeks to recommend strategic policy options geared towards enhancing sophistication level of Ulsan City's major export industries in the Republic of Korea. Ulsan's major export industries, including shipbuilding, automobile and petrochemical industries, turn out to be based mostly on low to medium technology with low R&D intensity suggesting relatively low level of product sophistication. Using a recent Eurostat high-tech industry classification table which suggests 9 high-tech industries, the paper identifies Ulsan's chemical industry as the only RCA industry. Focusing on chemical industry products at HS 6-digit level, specific products are identified at the efficiency frontier for future policy considerations.

• Bulletin of the Korean Chemical Society
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• v.17 no.2
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• pp.179-182
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• 1996

Hydrodediazoniation product (3a-d) was found to be the major product in the reaction of arenediazonium tetrafluoroborate (1a-d) with triethylamine (2) in methanol under nitrogen at room temperature. A quantitative study on the title reaction was investigated in detail and two remarks were noteworthy. One was the linear increase in the yield of 3a-d by increasing the molar concentration of 2 until equimolar concentration was reached between 1a-d and 2. The other was the suppression of the formation of 3a-d in the presence of oxygen. Based on these results, the title reaction was better understood by 1:1 electron transfer reaction between reactants (1a-d and 2) rather than by radical chain mechanism proposed in the reaction of arenediazonium tetrafluoroborate and triphenylphosphine.

• Bulletin of the Korean Chemical Society
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• v.16 no.3
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• pp.202-204
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• 1995

The ultraviolet photochemistry of N,N'-bis(salicylidene)ethylenediamine copper(II), Cu(sal)2en, was investigated with low pressure mercury lamp. Redution of Cu(Ⅱ) and formation of Cl- were shown on 254 nm irradiation both for aerated and deaerated chlorinated hydrocarbon solvent such as CH2Cl2, chloroform, and 1,2-dichloroethane. Relatively long lived $({\tau}=100{\mu}sec)$ intermediate was detected by flash photolysis. Overall photo-process can be described as the formation of Cl- and new copper complex, product(1) by chlorohydrocarbon mediation, photoinduced reduction by abstraction of halogen from solvent, followed by redox induced substitution of axial ligand with chlorine. Product(1) is possibly Cu(III) chlorosalicylaldeimido complex and cyclic -CH2CH2- moiety is absent in the structure. 247nm band of Cu(sal)2en should contain ligand to metal charge transfer character.

• Bulletin of the Korean Chemical Society
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• v.14 no.2
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• pp.287-291
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• 1993

Catalytic iminohydroacylation has been achieved by the reaction of aldimine 1 and 1,5-hexadiene (2a) with Wilkinson's complex as catalyst. Compounds 7a, 8a and 9a were obtained as final product after hydrolysis of the resulting iminohydroacylation products 4a, 5a and 6a. Depending on the reactant ratio (2/1), the ratio of products were changed dramatically : As the 2/1 ratio was increased, 7a is the major product after hydrolysis while 8a is the major with an 1/1 ratio of 2/1. The mechanism of the formation of 5a is determined by the reaction of 1 and 2b under the identical reaction conditions. Considering that 5a may not be formed from the hydroiminoacylation of 14a since 5b cannot be formed from that of conjugate diene 14b generated from isomerization of 2b, 5a must be formed from the reaction of 4a and 10 by addition-elimination mechanism.

• Bulletin of the Korean Chemical Society
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• v.6 no.5
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• pp.291-295
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• 1985

The efficiency of photosensitization of methyl linoleate (ML) oxidation by N-acetyl-L-trypophan(NAT) and 3-methyl indole(scatole) was markedly enhanced by increased concentration of ML in ethanol solution. The fluorescence intensities of sensitizers were observed to be quenched by ML, indicating that ML interacts with the indole excited singlet state. The inhibition of photosensitization by azide demonstrated a possible role of singlet oxygen in the photosensitization. The steady state kinetic treatment of azide inhibition of photosensitization was expected to show linear increase of reciprocal yield of ML oxidation product vs. reciprocal ML concentration at constant azide concentration, but the actual slope was nonlinear. This indicates another competing reaction involved in the photosensitization, As a possible competing reaction, electron transfer from ML to the excited sensitizer was proposed, since the measured fluorescence quenching rate constant closely resembled electron transfer rate constant determined from ML concentration dependence of oxidation product formation.

• Bulletin of the Korean Chemical Society
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• v.17 no.2
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• pp.153-158
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• 1996

The synthesis of common skeleton of podosporin A and aureol was studied through cationic olefin cyclization as a key step. The generation of thermodynamic silyl enol ether or enol acetate under known conditions gave regioselectivity of 88:12. The enolate alkylation of 2,3-dimethylcyclohexanone with 2,5-dimethoxybenzyl bromide at the more substituted site via lithium enolate gave poor yield. In this case an organozincate or an ammonium enolate also proved to be ineffective or not practical in terms of yield. Side chain elongation of the substituted cyclohexanone 13 through Grignard reaction, Wittig reaction, or Shappiro reaction did not proceed because of steric hindrance and side reactions. However, Stille coupling reaction via enol triflate produced the desired product 18 in high yield. The advanced intermediate 22, which was efficiently synthesized from 18, produced 24 instead of the desired product under a cationic olefin cyclization condition, indicating that the cyclization occurred in a stepwise mannervia the organomercury intermediate 23.

• Bulletin of the Korean Chemical Society
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• v.9 no.3
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• pp.161-164
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• 1988

Infrared multiphoton decompositions (IRMPD) of $BrCH_2CH_2CH_2CH_2Cl$ were studied by using the pulsed $CO_2$laser. At 0.3 J laser energy the experimentally observed product ratios could be reasonably explained by the RRKM calculation with initial excitation energy of ca. 80 Kcal/mol. The pressure dependence of product yields led us to conclude that the collisional deactivation by the inert gas decreased the yield of low energy dissociation channel more significantly.

• Food Science and Preservation
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• v.5 no.3
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• pp.305-314
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• 1998

In the drying process, many undesirable physicochemical changes occur that influence dried food product qualities. Pretreatments method is used to reduce the deterioration of dried food product qualities such as color, flavor, texture, rehydration ability and retention of nutrients. The methods of pretreatments are blanching, chemical treatment and osmotic dehydration. Osmotic dehydration is a water removal process which is based on placing foods in a concentrated osmotic solution or in a dry osmotic material. A large number of process variables have a significant effect on process and final product quality. In order to improve final product quality it is necessary to know the role of each process variable and understand the mecanisms throughout the process. Osmotic dehydration is a valuable processing tool with great future in minimal processing of fruits and vegetables.