• Bulletin of the Korean Chemical Society
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• v.12 no.6
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• pp.625-628
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• 1991

Using uniform flat plate-like samples of ZSM-5 zeolites, diffusion coefficients were measured volumetrically for the diffusion of xylene, ethyltoluene and diethylbenzene by direct measurement of sorption rate. Toluene disproportionation over H(100)-, K(72)-and Cs(82)-ZSM-5 at 773 K and toluene methylation, toluene ethylation and ethylbenzene ethylation over Cs(75)-ZSM-5 at 623 K were carried out. The selective formation of para xylene during the toluene disproportionation, presumably due to the increased tortuosity over Cs-ZSM-5, could be explained by smaller diffusion coefficient in Cs-ZSM-5 than in K-and H-ZSM-5. The para selectivity increased in the order; toluene methylation < toluene ethylation < ethylbenzene ethylation. As the chain length of the alkyl substituent in dialkylbenzenes is increased, the para selectivity of the products was improved. It may be attributed to the differences in the ratios of diffusion coefficient of para products to that of ortho ones. Diffusion coefficient of m-xylene was about 1 order of magnitude smaller than that of o-xylene.

• YAKHAK HOEJI
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• v.56 no.6
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• pp.390-394
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• 2012

A series of new pyridazinyl sulfoxides 3a~e and pyridazinyl sulfones 4a were synthesized for development of candidates to retain anticancer activity. The utility of sulfoxides and sulfones in both laboratory and industrial practice was quickly recognized, and these species have been extensively utilized, including as pharmaceutical intermediates and anticancer agents. Alkylthiopyridazines 2a~e were prepared from the 3,6-dichloropyridazine using allylthiolation with alkyl mercaptan. Sulfides could be oxidized to sulfoxides or sulfones using 1~3 equivalents of hydrogen peroxide as an oxidant. The oxidation of sulfoxides to sulfones was also accomplished with aqueous hydrogen peroxide. Formation of 3a~e and 4a was undertaken with stirring using 35% hydrogen peroxide at room temperature in acetic acid for 18~72 h. Synthetic compounds were identified using NMR spectrum.

• Bulletin of the Korean Chemical Society
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• v.6 no.5
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• pp.272-276
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• 1985

Various new kinds of biheterocyclic betaines were prepared by the reaction of 3-substituted-6,7-dihydro-5H-thiazolo[3,2-a]pyrimidine with electrophiles such as isothioyanates, isocyanates in aprotic solvents, respectively. The biheterocyclic betaines containing methyl group at 3-position of thiazole ring were obtained particularly in good yields at room temperature. These betaines were also reacted with alkyl halide to give quarternary ammonium salts. It was found that these betaines are dissociated in polar organic solvents depending on temperature. And new biheterocyclic compounds via ring transformation were prepared by the reaction of 8-phenyl (thiocarbamoyl)-3-phenyl-6,7-dihydro-5H-thiazolo[3 ,2-a]pyrimidinium-betaine with ${\alpha}$-halo kester ${\alpha}-halo$ ester and ${\gamma}-halo$ keto ester.

• Bulletin of the Korean Chemical Society
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• v.16 no.4
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• pp.363-369
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• 1995

Hydroiminoacylations of allyl and homoallyl alcohol and their derivatives with benzaldimine by Wilkinson's complex have been studied. All these terminal alkene derivatives except allyl alcohol were hydroacylated according to anti-Markownikoff's rule to give the corresponding linear alkyl compounds without showing oxygen directing effect, even though hydroiminoacylation of 3-acetoxy-1,5-hexadiene showed strong allyloxy directing effect over homoallyloxy directing effect in a 92:8 ratio. Solvolysis of 4-acetoxy-1-phenylbutan-1-one, previously prepared by hydroiminoacylation, in ethanol led to etherification giving 4-ethoxy-1-phenylbutan-1-one through neighbouring group participation, while that of 5-acetoxy-1-phenylpentan-1-one led to common transesterification giving 5-hydroxy-1-phenylpentan-1-one. Application of branched alkanols such as isopropanol and t-butanolin solvolysis of 4-acetoxy-1-phenylbutan-1-one underwent competition between etherification and transesterification.

• Journal of Life Science
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• v.24 no.12
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• pp.1325-1329
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• 2014

Gugija (Lycii chinese Miller) is traditionally consumed as a Chinese medicinal material in food, tea, or alcoholic beverages. Gugija has beneficial healthy components, but it produces an off-flavor during storage. This study compared the flavor components of fresh-dried Gugija and stale-dried Gugija. The flavor compounds in one fresh sample (sample 1) and one stale sample (sample 2) were extracted by the simultaneous distillation and extraction method. The concentrated aroma extracts were analyzed and identified by gas chromatography-mass spectrometry. Forty-five compounds, including 17 aldehydes, 8 alcohols, 6 terpene compounds, 4 esters, 3 ketones, and 3 pyrazines, were isolated in sample 1. Thirty-four compounds, including 12 aldehydes, 3 alcohols, 5 terpene compounds, 2 esters, 3 ketones, 3 pyrazines, and 1 acid, were isolated in sample 2. The main aroma components of sample 1 were 2-methyl butanal, 2-methyl propanol having sweet odor, and hexanal, (Z)-3-hexenol having grass odor, and phenyl acetaldehyde, benzyl alcohol having floral odor, and alkyl pyrazines having nutty odor. These compounds were decreased in sample 2, and several compounds containing isovaleric acid, which has a disagreeable, rancid-cheese odor were found newley.

• Korean Journal of Food Science and Technology
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• v.20 no.2
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• pp.157-163
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• 1988

The volatile compounds produced from the browning reaction of 0.5M DL-alanine and 0.5M D-glucose mixture using propylene glycol as a reaction medium were analysed by gas chromatography and gas chromatography-mass spectrometry and effects of temperature($100^{\circ}C,\;120^{\circ}C,\;140^{\circ}C$) and time(20min, 2hours) on the formation of volatile compounds were investigated. Browning reaction were rapidly increased as the reaction temperature and time increased. From methylene chloride extracts, twenty six compounds, including 7 alkyl pyrazines. 4 pyrroles, 3 furans, 1 furanone and 11 miscellaneous compounds were identified. The relative amounts of pyrazines, pyrroles and furans were markedly increased as reaction temperature and time increased. The results showed that caramel-like and burnt sugar-like aroma produced by alanine -glucose reaction must be mainly comprised of nitrogeneous heterocyclic such as pyrazines, pyrroles and oxygen heterocyclic compounds such as 2-hydroxy-3-methyl-2-cyclopenten-1-one and 2,5-dimethyl-4-hydroxy-3(2H)-furanone.

• Journal of Microbiology and Biotechnology
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• v.18 no.4
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• pp.676-681
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• 2008

To obtain a natural antioxidant from a marine biomass, this study investigated the antioxidative activity of methanolic extracts from the marine brown alga, Ishige okamurae collected off Jeju Island. A potent free radical scavenging activity was detected in the ethyl acetate fraction containing polyphenolic compounds, and the potent antioxidant elucidated as a kind of phlorotannin, diphlorethohydroxycarmalol, by NMR and mass spectroscopic data. The free radical scavenging activities of the diphlorethohydroxycarmalol were investigated in relation to 1,1-diphenyl-2-picrylhydrazyl (DPPH), alkyl, and hydroxyl radicals using an electron spin resonance (ESR) system. The diphlorethohydroxycarmalol was found to scavenge DPPH ($IC_{50}=3.41{\mu}M$) and alkyl ($IC_{50}=4.92{\mu}M$) radicals more effectively than the commercial antioxidant, ascorbic acid. Therefore, these results present diphlorethohydroxycarmalol as a new phlorotannin with a potent antioxidative activity that could be useful in cosmetics, foods, and pharmaceuticals.

• Journal of the Korean Chemical Society
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• v.48 no.4
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• pp.385-393
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• 2004

2-Ethoxycarbonyl-3-methylquinoxaline 1,4-dioxide (8) was synthesized from benzofuroxan and ethyl acetoacetate. The reaction of compound 8 with hydrazine hydrate or selenium dioxide gave 2-hydrazinocarbonyl-3-methylquinoxaline 1,4-dioxide (9) or 2-ethoxycarbonyl-3-formylquinoxaline 1,4-dioxide (10), respectively. The reaction of compound 9 with alkanoyl chlorides, benzoyl chlorides, heteroacyl chlorides, and benzenesulfonyl chlorides afforded 3-methyl-2-(substituted hydrazinocarbonyl)quinoxaline 1,4-dioxides (11-14), respectively. The reaction of compound 9 with sodium azide gave 2-azidocarbonyl-3-methylquinoxaline 1,4-dioxide (15), and then its refluxing in dioxane/alcohols resulted in the Curtius rearrangement to give N-(3-methyl-1,4-dioxoquinoxalin-2-yl)-alkyl carbamates (16). The reaction of compound 15 with substituted anilines afforded 2-(3-substituted phenylureido)-3-methylquinoxaline 1,4-dioxides (17). The reaction of compound 10 with benzoic hydrazide or substituted anilines provided quinoxaline 1,4-di-oxides (18, 19), respectively. The herbicidal and fungicidal activities of the synthesized compounds were investigated.

• Journal of the Korean Applied Science and Technology
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• v.34 no.1
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• pp.142-151
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• 2017

Cationic surfactants have a bactericidal effect and the study for effective development of them became important parts in the industry. There have been increasing researches that focus on the development of products having not only outstanding features but also safety and biodegradability. In this work, novel ester-type cationic surfactants were obtained via Michael addition reaction. Intermediates were quantitatively prepared by the Michael addition reaction between alkyl acrylate and amine compounds under mild conditions without solvent and catalyst. The intermediates were quaternized with dimethyl sulfate. HQ21 with two hydrophobic groups and a hydrophilic group and HQ22 with two hydrophobic groups and two hydrophilic groups were obtained. The structures of the products were characterized by 1H-NMR, HR-MS and FT-IR and biodegradability of the products were tested.

• Journal of the Korean Chemical Society
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• v.45 no.4
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• pp.325-333
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• 2001

The 4-substituted tetrazolo[1,5-a]quinoxalines were synthesized from 4-chlorotetrazolo-[1,5-a]quinoxaline(8) or 4-hydrazinotetrazolo[1,5-a]quinoxaline(9). Refluxing of the tetrazolo[1,5-a]quinoxaline(12) in N,N-dimethylformamide gave the 1,2,4-triazolo[3,4-c]tetrazolo[1,5-a]quinoxaline(13), which was also obtained by the reaction of compound 9 with ethyl chloroformate in N,N-dimethylformamide. The reaction of compound 9 with isothiocyanates in ethanol provided the tetrazolo[1,5-a]quinoxalines(14), whose reaction with dimethyl acetylenedicarboxylate afforded the tetrazolo[1,5-a]quinoxalines(15). The tetrazolo [1,5-a]quinoxalines(18) were obtained by the reaction of compound 9 with alkyl (ethoxymethylene)cyanoacetates. Some of the compounds showed antibacterial, antifungal or algicidal activities against some strains.