• Journal of the Korean Chemical Society
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• v.38 no.5
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• pp.377-381
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• 1994

New bis-crown ethers containing siloxane chain were synthesized. 1,3-Bis(trimethylsiloxy)-1,3-dimethyl-1,3-dipentaoxacyclohexadecamethyl disiloxane (1) was synthesized by reaction of 3-methylene-16-crown-5 (8) with 1,3-bis(trimethylsiloxy)-1,3-dimethyl disiloxane (10) in the presence of Pt catalyst. 1,1,3,3,5,5-Hexamethyl-1,5-dipentaoxacyclohexadecamethyl trisiloxane (2) was synthesized by the reaction of crown ether (8) with 1,1,3,3,5,5-hexamethyl trisiloxane (11) in the presence of Pt catalyst. 3-Methylene-13-crown-4 (7), 3-methylene-16-crown-5 (8), and 3-methylene-19-crown-6 (9) were synthesized by the reaction of triethylene glycol (3), tetraethylene glycol (4), and pentaethylene glycol (5) respectively with 3-chloro-2-chloro-methyl-1-propene (6) in the presence of NaH.

• Korean Journal of Food Science and Technology
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• v.26 no.3
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• pp.255-260
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• 1994

Four types of soybean paste(Doenjang), using traditional meju, koji, natto meju and mixture of koji and natto meju, were manufactured and fermented for 90 days. Analyzed volatile flavor components by GC-MS were confirmed to be thirty-six components including 5 alcohols, 5 aldehydes. 8 ketones, 3 acids, 9 esters and 6 miscellaneous ones. Traditional soybean paste tested had 29 components, koji and koji-natto soybean paste $26{\sim}24$ and natto soybean paste had 20 ones. Alcohol was found to be the most abundant volatile flavor components in all samples group. Traditional soybean paste had higher ratio of carbonyl to ester than any other types of soybean paste while koji-natto soybean paste had the lowest ratio of their components. The newly identified five volatile flavor components were 3-ethoxy-l-propene, dihydro-2-methyl-3-furanone. 1-hydroxy-2-propanone, 1-(2-furanyl)ethanone and 2-acethyl ethylhexanoate.

• Food Science and Preservation
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• v.4 no.3
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• pp.295-300
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• 1997

The water extract of mustard seed was fractionated by solvents with an increase of polarity, and antimicrobial activities of each extracts were examined, and volatile compounds of each extract were identified by GC-MS. When the water extract was fractionated with solvents, the antimicrobial activities were high in the order of chloroform, ethylacetate, hexane, butanol and aqueous layer. In chloroform fraction, 16 volatile compounds, including 2 isothiocyanates such as 3-isothiocyanato- 1-propene and 4-isothiocyanato- 1-butane, 1 nitrile and 4 acids were identified, their contents were higher than other fractions. Twelve, 10, 4 and 7 volatile compounds were identified in ethylaceate, hexane, butanol and water fractions, respectively. The volatile compounds were considerably less in the fractions of butanol and water than others.

• Journal of Korean Society for Atmospheric Environment
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• v.14 no.2
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• pp.153-160
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• 1998

The concentrations of volatile organic compounds (VOCs) in the atmosphere were measured from the Yochon Industrial Estate and compared with those from Tongkwangyang and Seoul. The first important phenomenon observed in the air of Yochon was high concentrations of alkenes and in particular, ethylene and propene. For most dominant species, their means and standard deviations were high simultaneously. Concentrations of several major aliphatic species exhibited a similar pattern of diurnal variation, however, with different species combination on each day. Concentrations of several hazardous aromatic species also exhibited a similar pattern of diurnal variation on the same day, which was different from that observed in the diurnal variation of major aliphatic species. It was interpreted that some species were intermittently released from relevant processes. It was also understood that high concentrations and variations of VOC species in Yochon were localized and not related to high average concentrations of ozone in Yochon and Tongkwangyang areas.

• Carbon letters
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• v.8 no.1
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• pp.25-29
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• 2007

The carbon brake discs were manufactured by densification the carbon fiber preform using PG-CVI technology with Propene as a carbon precursor gas and Nitrogen as a carrier gas. The densities of carbon brake discs were tested at different densification time. The results indicate that the densification rate is more rapid before 100 hrs than after 200 hrs. The CTscanning image and the SEM technology were used to observe the inner subtle structure. CT-images show the density distribution in the carbon brake disc clearly. The carbon brake disk made by PG-CVI is not very uniform. There is a density gradient in the bulk. The high-density part in the carbon brake is really located in the friction surface, especially in the part of inner circle. This density distribution is most suitable for the stator disc.

• Bulletin of the Korean Chemical Society
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• v.13 no.1
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• pp.65-70
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• 1992

The hindered internal rotation effect of methyl group on chemical reaction was studied for cis-trans isomerization reaction of 1-bromopropene system using RRKM technique. A comparative study of the isomerization rates was also performed between the rigid and allowed internal rotations. The calculated rate of rigid cis-trans isomerization of 1-bromopropene was shown to be three times higher than its other halogenated propene homologues with its internal rotations and found to be in good agreement with experimental observations. These findings could be explained reasonably well in terms of the differences of the rotational barrier heights among halogenated propenes and correlated with the relatively low internal rotation barrier of cis-1-bromopropene, 230 cal/mol, compared to those of other cis-1-halopropenes, 700-800 cal/mol, and trans-1-halopropenes, 2.0-2.4 kcal/mol.

• Bulletin of the Korean Chemical Society
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• v.16 no.5
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• pp.443-449
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• 1995

N-(Isopropyloxycarbonyloxy)maleimide (iPOCMI) has been synthesized and polymerized to give both the homopolymer and copolymers with substituted styrenes. These polymers were readily deprotected by thermolysis of the isopropyloxycarbonyl (iPOC) groups to provide the corresponding N-hydroxymaleimide (HOMI) polymers. The homopolymer and styrenic copolymers of iPOCMI were radically obtained in higher conversion and higher molecular weight than those obtained by direct polymerizations of N-hydroxymaleimide. The homopolymer of iPOCMI was transformed into poly(N-hydroxymaleimide)P(HOMI) by thermolysis of iPOC groups at 205 $^{\circ}C$ with concurrent release of propene and carbon dioxide. The copolymer of iPOCMI and styrene was thermally deprotected to the copolymer of HOMI and styrene at 235 $^{\circ}C.$ The mass loss was 28% and the Tg of the resulting copolymer was 250 $^{\circ}C.$ The thermal deprotection readily provided the desired, polar HOMI polymers which have Tgs above 240 $^{\circ}C.$ The deprotection was accompanied by large changes in aqueous base solubility.

• Bulletin of the Korean Chemical Society
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• v.7 no.4
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• pp.279-282
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• 1986

The MNDO calculations were performed in order to investigate the gas-phase reaction mechanism of 2-propene-1-al oxide, as a model compound of dypnone oxide(1,3-diphenyl-2-butene-1-one oxide) with the chloride ion. Optimized geometries and heats of formation for two probable concerted pathways, CHO and H migration, were determined and their activation energies were obtained. MO results show that although the formyl migration is thermodynamically more favorable than the hydride migration, the latter kinetically predominates over the formyl migration, which is contrary to the established migrating preferences. It is concluded that the hydride migratory propensity is catalyzed by the chloride ion by reducing the capability of the carbonyl ${\pi}$ bond to participate in the migration.

• Food Science and Preservation
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• v.23 no.3
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• pp.369-377
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• 2016

This study was conducted to investigate the effects of superheated steam (SHS) on volatile compounds and the quality characteristics of onion. Onion samples were treated by SHS at various steam temperatures ($100{\sim}300^{\circ}C$) for 1 min. Thiosulfinates and pyruvic acid were reduced by SHS treatment. The absorbance values obtained for thiosulfinates, the odor-causing compounds in onions, treated by were 0.889, 0.085, 0.049, 0.049, and 0.045, while that of the untreated control sample was 1.587. The pyruvic acid contents of onions treated by SHS were 7.57, 5.85, 1.66, 0.47, and 0.26 mg/mL, while that of the untreated control sample was 8.00 mg/mL. Volatile compounds such as, dipropyl trisufide, 1,3-propanedithiol, methyl thiirane, methyl propyl trisulfide, diallyl disulfide, 1-(methylthio)-1-propene, 1,1-thiobis-1-propene, 1,1-sulfinyl bispropane, dimethyl tetrasulfide, methyl propenyl disulfide, dimethyl trisulfide, and diallyl disulfide were reduced by SHS treatment. The results showed that antioxidant activities in the of onion samples were improved by SHS treatment. The hardness and chewiness of onions treated by SHS were significantly lower than those of the untreated control onion sample. Sensory evaluation suggested that SHS could help lower off-flavors in and enhance the palatability of onions. These results suggest that the application of SHS treatment to onions can decrease their off-flavors, change their textural attributes, and promote their sensory properties.

• Journal of the Korean Society of Food Science and Nutrition
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• v.31 no.4
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• pp.566-571
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• 2002

Volatile flavor compounds in Alaska pollack sik-hae during fermentation at 5$^{\circ}C$ were analyzed by liquid-liquid continuous extraction (LLCE) and gas chromatography/mass spectrometry (GC/MS) methods. Sixty five volatile compounds were detected in Alaska pollack sik-hae during fermentation. These compounds were composed mainly of 11 S-containing compounds, 13 alcohols, 13 acids, 4 aldehydes, 4 ketones, 6 terpenes,4 aromatic compounds and 10 miscellaneous compounds. Among these, 9 S-containing compounds (3-(methylthio)-1-propene, dimethyl disulfide, diallyl sulfide, methylallyl disulfide, methyl-(E) -propenyl disulfide, dimethyl trisulfide, 2 diallyl disulfide isomers and diallyl trisulfide), 2 acids (acetic acid and butanoic acid), 2 ketones (2, 3-butanedione and 6-methyl-5-hepten-2-one) and 2 esters (ethyl formate and ethyl acetate) were significantly increased during fermentation (p<0.05), and these compounds were suspected to affect on the odor of Alaska pollack sik-hae.