• Bulletin of the Korean Chemical Society
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• 제32권1호
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• pp.225-228
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• 2011

Poly(4-vinylpyridine)-supported $Br{\phi}nsted$ acids (P4VP-HX) were prepared by wet impregnation technique. These supported acids were found as efficient heterogeneous green catalysts for acetylation of alcohol, amine and phenol with different catalytic activities. The wide application of P4VP-HX as reusable solid acid catalyst in organic reactions is possible because of its simple preparation and handling, stability, simple work up procedure.

• 한국응용과학기술학회지
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• 제27권4호
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• pp.475-481
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• 2010

Elution effect was studied by the reactions between Electric arc furnace(EAF)dust and conc. or dil. sulfuric acid for the purpose of recoverying of the useful metals afterwards. The methods of mixing with acids and EAF dust for the elutions were depend on the ratios of acid/EAF dust. Experimental results showed that increased the ratios of sulfuric acids, decreased the elution effects are on the Zn, Fe and Mn, and conc. sulfuric acid showed higher elution effects than dil. sulfuric acids for the all metals. But in case of Pb, dil. sulfuric acid showed higher elution effects than conc. sulfuric acids conversely. Furthermore, the reason of the extreamly low quantities of eluted Pb is caused by the low solubilities by sulfuric acids compared to the other metals, as the results of the insoluble Pb is removed by the process of filtering.

• 한국연초학회지
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• 제4권2호
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• pp.75-80
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• 1982

During the process of curing of the tobacco (Nicotiana tabacum L. ) leaves the concentration change of Nonvolatile organic acids and Higher fatty acids of the flue-cured tobacco leaves was observed. The contents of Nonvolatile organic acids in flue-cured tobacco leaves were as follows, malic> oxalic>malonic>citric>succinic acid. Higher fatty acids was linolenic>Palmitic>oleic >stearic$\geqq$linoleic acid, Citric acid content of last curing time was increased about 4~5 times in compare to before curing tobacco. It was concluded that significant changes of three variety flue-cured tobacco but a significant difference was observed in the composition of Daegu gold variety.

• Bulletin of the Korean Chemical Society
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• 제24권4호
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• pp.467-472
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• 2003

Optically pure α-mono- and α, α-disubstituted β-amino acids were conveniently prepared in four steps and in 27-40% overall yields from the correspondingly substituted racemic β-hydroxy acids that can be readily obtained from diethyl malonate. In the synthesis, (S)-phenylethylamine has been used as a resolving agent and as a source of the amino group in the β-amino acids.

• Bulletin of the Korean Chemical Society
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• 제10권6호
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• pp.491-495
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• 1989

Resolution of enantiomers of DNS-amino acids has been achieved by a reversed phase liquid chromatography with an addition of a copper(Ⅱ) complex of N-benzyl-L-hydroxyproline to the mobile phase. N-Benzyl-L-hydroxyproline was prepared and used as a chiral ligand of copper(Ⅱ) chelate for the optical resolution. The pH and the concentration of copper(Ⅱ) chelate, organic solvent, and buffer agent in the mobile phase all affect the optical resolutions of dansyl amino acids. The elution orders between D and L-DNS-amino acids were different depending on the structure of the side chain of the amino acids. The retention mechanism for the chiral separation of the dansyl amino acids can be illustrated by the equilibrium of ligand exchange and by hydrophobic interaction with $C_{18}$ stationary phase. The chiral separation can be illustrated with cis and trans effect of the ligand exchange reaction.

• Bulletin of the Korean Chemical Society
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• 제13권3호
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• pp.280-285
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• 1992

Enantiomeric separation of free amino acids has been achieved by a reversed phase liquid chromatography with addition of a Cu(Ⅱ) complex of N-alkyl-L-proline (alkyl: propyl, pentyl or octyl) to the mobile phase. The amino acids eluted were detected by a postcolumn OPA system. N-alkyl-L-proline was prepared and used as a chiral ligand of Cu(Ⅱ) chelate for the enantiomeric separation. The concentration of the Cu(Ⅱ) chelate, the organic modifier and pH affect the enantiomeric separation of free amino acids. The retention behaviour, varied with change in pH and the concentration of the Cu(Ⅱ) chelate, was different compared with those of the derivatized amino acids. The elution orders between D- and L-forms were consistent except histidine showing that L-forms elute earlier than D-forms. The retention mechanism for the enantiomeric separation can be illustrated by the stereospecificity of the ligand exchange reaction and the hydrophobic interaction between the substituent of amino acids and reversed phase, $C_18$.

• Journal of Nutrition and Health
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• 제11권3호
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• pp.21-24
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• 1978

나무딸기의 화학적 성분의 조성(組成)을 알기 위하여 유리 아미노산은 아미노산 자동분석계, 유기산은 GC 유리당은 ppC를 통하여 분석 조하여 다음과 같은 결론(結論)을 얻었다. 1. 유리아미노산은 18종(種) 발견되었으며 특히 lysine의 함량(含量)이 많았다. 필수(必須)아미노산을 고르게 함유하여 타 과실에 비하여 좋은 아미노산 조성(組成)을 이루고 있다. 2. 유기산은 citric acid, tartaric acid, maleic acid, fumaric acid가 발견 되어졌으며 일반적으로 그 함량은 적었다. 3. 당은 glucose, fructose, mannose, maltose lactose등을 함유하고 있다.

• 한국조리학회지
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• 제23권5호
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• pp.1-11
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• 2017

The objectives of this study were: 1) to examine the contents of chemical composition (chlorogenic acids, caffeine, free acids, and free sugars) and 2) to evaluate the sensory attributes (sourness, bitterness, and sweetness) of brewed coffee as affected by two roasting conditions such as varied in the roasting time with the same roasting temperature (RT) and with same color and yield (CY). Quantitative analysis of chemical components was performed using high-performance liquid chromatography (HPLC) system, and quantitative descriptive analysis (QDA) was conducted to analyze sensory attributes. Based on the results of chemical analysis, chlorogenic acids were significantly different (p<0.05) in the short term roasted samples (RT 240 and CY 240), but there was no significant difference in caffeine contents (p>0.05). Organic acid levels were different between RT and CY coffee samples. RT 240 coffee had the most level in organic acids and the longer the roasting time of coffee, the lesser the level of organic acids in coffee was found. However, there was no significant difference in CY coffee (p>0.05). The results of sensory evaluations show that the degree of roasting changed according to the roasting time despite of the roasting temperature. Long term (RT 80) coffee was relatively bitter while short term (RT 240) coffee was relatively sweeter. Also, there was no significant difference (p>0.05) in the sensory characteristics (bitterness and sweetness) of CY coffee although they were roasted at different temperatures. Therefore, the current study concluded that better understanding of proper roasting time and temperature improves the quality of brewed coffee.

• Bulletin of the Korean Chemical Society
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• 제31권7호
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• pp.1887-1890
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• 2010

Cross-linked polystyrene supported aluminium triflate (Ps-Al(OTf)$_3$) was found to be an efficient and chemoselective heterogeneous Lewis acid catalyst for the direct conversion of arenes to sulfones using sulfonic acids as sulfonylating agents. The solid acid catalyst is stable (as a bench top catalyst) and can be easily recovered and reused without appreciable change in its efficiency.

• Bulletin of the Korean Chemical Society
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• 제27권11호
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• pp.1791-1794
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• 2006

We have introduced a new enantioselective receptor 1 by incorporation of chiral building blocks to the previously reported carboxylate selective receptor 2. Binding studies carried out using $^1H$ NMR revealed that the receptor 1 showed moderate enantioselectivity with a general preference for D-amino acids and a highest enantioselectivity for leucine among the amino acids we investigated.