• 대한화학회지
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• 제47권4호
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• pp.432-436
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• 2003

• 한국자기공명학회논문지
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• 제21권1호
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• pp.1-6
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• 2017

Enhancements in NMR sensitivity have been the main driving force to extend the boundaries of NMR applications. Recently, techniques to shift the thermally populated nuclear spin states are employed to gain high NMR signals. Here, we introduce a technique called photochemically induced dynamic nuclear polarization (photo-CIDNP) and discuss its progresses in enhancing the solution-state NMR sensitivity.

• 약학회지
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• 제24권3_4호
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• pp.151-157
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• 1980

Color transition mechanism of shikonin as an acid-alkali indicator was studied. It was confirmed that the presence of phenolic hydroxy radical was essential for the color change of shikonin. But in accordance with shikonin sodium salt (blue color), which was presumed to make chelation as six membered rings. Shikonin in alkaline solution, by dissociated phenolic protons of naphthoquinone nucleous, converted to the corresponding anion and instead of disappearance tautomerization, electron delocalization occurred and an additional pair of nonbonding electrons in the anion was available for interaction with .phi. electron system of the ring with further extension of the conjugation. It was responsible for its blue color(corresponding color: orange) with needs less energy difference (${\phi}{\rarw}{\phi}^{*}$) because of conjugation extension. Shikonin sodium salt seems to have similar nuclear structure as shikonin anion.

• Bulletin of the Korean Chemical Society
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• 제12권6호
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• pp.678-681
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• 1991

The Wittig-oxy-Cope rearrangements of deprotonated diallyl ether, I, $CH_2={\bar{C}}H-CH-O-CH_2-CH=CH_2$, have been investigated theoretically by the AM1 method. A two step mechanism forming a Wittig product ion, II, $(CH_2=CH)$ $(CH_2=CH-CH_2)$ $CHO^-$, through a radical-pair intermediate was found to provide the most favored reaction pathway in the Wittig rearrangement. The subsequent oxy-Cope rearrangement from species II also involves a two step mechanism through a biradicaloid intermediate. The intramolecular proton transfer in I (to form $CH_2=CH-CH_2-O-{\bar{C}}H-CH=CH_2$) is a higher activation energy barrier process compared to the Wittig and oxy-Cope rearrangements and is considered to be insignificant. These results are in good agreement with the condensed-phase as well as gas-phase experimental results.