• 대한화학회지
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• 제38권8호
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• pp.552-561
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• 1994

아조벤젠 유도체의 시스→트란스 열적 이성질화 반응을 연구하였다. 밀고-당기는 아조벤젠은 이성질화 반응속도의 용매효과가 큼이 확인되었고 이러한 현상으로 밀고-당기는 아조벤젠은 회전 메카니즘에 의해서 이성질화 반응이 일어남을 알 수 있다. 밀고-당기는 아조벤젠이 아닌 화합물은 이성질화 반응속도의 용매효과가 거의 없음이 관찰되었으므로 반전 메카니즘에 의해서 이성질화 반응이 일어남을 확인하였다.

• Journal of Photoscience
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• 제10권1호
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• pp.71-79
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• 2003

Recent advances in photosensitized enantiodifferentiating isomerization and cycloaddition reactions of cycloalkenes (other than cyclooctene) and cycloalkadienes are reviewed.

• Bulletin of the Korean Chemical Society
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• 제5권5호
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• pp.199-201
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• 1984

It has been found that $Rh(ClO_4)(CO)(P(C_6H_5)_3)_2$ catalyzes the hydrogenation and isomerization of soybean oil at room temperature under the atmospheric pressure of hydrogen. The hydrogenation occurs at the olefinic groups to produce saturated groups leaving the ester groups intact, and the isomerization converts $-CH = CH- CH_2-CH = CH-$ units to conjugated dienes and the dienes separated by more than two $-CH_2-$ groups. The rate of the hydrogenation is faster than that of the isomerization.

• Bulletin of the Korean Chemical Society
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• 제10권4호
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• pp.360-362
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• 1989

Catalytic isomerization of unsaturated alcohols to the corresponding carbonyl compounds with$Rh(ClO_4)(CO)(PPh_3)_2\;(1)\;and\;[Rh(CO)(PPh_3)_3]ClO_4$ (2) is faster under hydrogen (where hydrogenation also occurs to give saturated alcohols) than under nitrogen. The isomerization under hydrogen seems to occur through an alkylhydridorhodium(III) complex which also undergoes reductive elimination to give hydrogenation products, saturated alcohols. The isomerization under hydrogen is faster with 2 than with 1, which is understood by acceleration of the last step, enol formation by $PPh_3$ dissociated from 2 and present in the reaction mixture when 2 is used as catalyst. Relative rates of the isomerization observed for different unsaturated alcohols are interpreted by steric effects of substituted groups and numbers of hydrogens to be abstracted by the rhodium of the intermediate, alkylhydridorhodium(III) to undergo the reductive elimination to give enol which is then rapidly converted into a carbonyl compound. It has been observed that the hydrogenation is relatively significant when reactions occur slowly whereas the isomerization is predominant when reactions proceed rapidly.

• 공업화학
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• 제18권1호
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• pp.36-40
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• 2007

헤테로폴리산 촉매를 이용하여 endo-tetrahydrodicyclopentadiene 및 endo-tetrahydrodi(methylcyclopentadiene)의 이성화반응에 관한 연구를 행하였다. 이성화반응에 의해 endo 형태를 exo 형태의 화합물로 제조하였다. 기존의 이성화촉매인 알루미늄 클로라이드의 문제점을 개선하기 위하여 헤테로폴리산의 적용을 시도하였다. Keggin 형태의 헤테로폴리산 촉매인 $H_3PW_{12}O_{40}$에서 수소원자 2.5개 대신에 cesium으로 치환시 촉매활성이 가장 높았다. Cesium으로 치환된 헤테로폴리산 촉매 사용시 기존의 알루미늄클로라이드 촉매보다 이성화반응속도가 빠른 것을 확인하였고, 반응온도, 시간에 따른 tetrahydrodicyclopentadiene 및 tetrahydrodi(methylcyclopentadiene)의 반응성을 비교하였다.

• Preventive Nutrition and Food Science
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• 제7권2호
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• pp.179-183
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• 2002

Lycopene as a natural antioxidant may provide protection against a broad range of epithelial cancers and chronic diseases. Lycopene concentrate extracted from tomatoes can be used as functional food. Lycopene would undergo degradation via isomerization and oxidation under different processing conditions, which impact its bioactivity and reduce the fuuctionality for health benefits. Heat and light induce lycopene oxidation and isomerization of all-trans form to cis form. The effects of thermal treatment and light irradiation on the stability of lycopene were determined. Results have shown that lycopene stability depends on the extent of oxidation and isomerization. Cir-isomers are less stable than trans-isomers. The level of cis-isomers increased as treatment time increased but only for a short period during the beginning of the treatment. The major effect of thermal treatment and light irradiation was a significant decrease in the total lycopene content. A true assessment of health benefits of lycopene concentrate depends on the lycopene content and the composition of all trans-isomers and cia-isomers.

• Bulletin of the Korean Chemical Society
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• 제29권4호
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• pp.761-766
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• 2008

Photoresponsive arylether dendrimers Bis-azo-Gn(3,5) 1a-1c and Bis-azo-Gn(3,4,5) 2a-2c (n = 1-3) with an azobenzene unit at the core and several vinyl groups (3,5-bis(but-3-enyloxy)phenyl groups or 3,4,5-tris(but-3- enyloxy)phenyl groups) at the periphery have been prepared. Their structures and reversible trans-cis isomerization behaviors have been investigated by $^1H$-NMR, $^{13}C$-NMR, MALDI-TOF-Mass, and UV-vis spectra. All six azobenzene-cored dendrimers carried out very fast trans $\rightarrow$ cis photoisomerization on irradiation of 350 nm light and reached to the photostationary state within 180 s. During the dark incubation, slow thermal back reversion from cis to trans form is observed for all six dendrimers and is completed within 3 days for 1a-1c and 1 day for 2a-2c. Isomerization efficiency decreases with increasing generation. However, the initial reaction rates of both trans $\rightarrow$ cis photochemical isomerization and cis $\rightarrow$ trans thermal isomerization increases significantly with increasing generation for dendrimers for 1a-1c but only slightly for 2a-2c.

• Bulletin of the Korean Chemical Society
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• 제34권11호
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• pp.3249-3252
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• 2013

We have explored the potential energy surface for the isomerization of the aniline (AN) radical cation to the 2-, 3-, and 4-methylpyridine (picoline, MP) radical cations using G3 model calculations. The isomerization may occur through the 1H-azepine (7-aza-cycloheptatriene) radical cation. A quantitative kinetic analysis has been performed using the Rice-Ramsperger-Kassel-Marcus theory, based on the potential energy surface. The result shows that isomerization between $AN^{+\bullet}$ and each $MP^{+\bullet}$ hardly occurs before their dissociations.

• Bulletin of the Korean Chemical Society
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• 제26권8호
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• pp.1190-1196
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• 2005

Halopyrroles, N-substituted 2-halopyrroles were prepared by halogenation of N-substituted pyrroles with NBS, NCS, or surfuryl chloride. N-Substituted 3-halopyrroles were synthesized by acid-catalyzed thermal and photochemical isomerization reactions of N-substituted 2-halopyrroles. Both the thermal and photochemical reactions were acid-catalyzed. For the acid-catalyzed isomerization, a mechanism of [1,3] bromine shift followed by deprotonation is operated. For the acid-catalyzed photoisomerization, an excited triplet state of 2-protonated N-benzyl-2-halopyrrole produces an intermediate N-substituted pyrrole complex with halonium ion which is equilibrated with N-substituted pyrrole plus halonium ion, and then the halonium ion newly adds to 3-position of N-substituted pyrrole followed by deprotonation to afford N-benzyl-3-halopyrrole.

• Bulletin of the Korean Chemical Society
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• 제25권1호
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• pp.106-108
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• 2004

In this paper we have determined the thermodynamic parameters for the isomerization between the ${\alpha}$-cis and the ${\beta}$-cis isomers in vanadium(V)-propylenediaminetetraacetate complex in water by $^{51}V$ NMR spectroscopy. In addition, the effects of organic solvents (methanol, formamide and dimethylsulfoxide) and inorganic salts (NaCl, $NaClO_4\;and\;NH_4Cl$) on the isomerization in solution have been investigated.