• Macromolecular Research
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• v.14 no.3
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• pp.354-358
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• 2006

Polybutadiene (BR) was pyrolyzed at $540-860^{\circ}C$ and the effect of pyrolysis temperature on variations in the relative abundance of the major pyrolysis products (C4-, C5-, C6-, C7-, and C8-species) was investigated. Formation of the C4-, C5-, C6-, and C7-species competed with that of the C8-species. Relative intensity of the C8-species decreased with increasing pyrolysis temperature, while that of the C5-, C6-, and C7-species increased. Pyrolysis paths were became more complicated with increasing pyrolysis temperature. We suggested the operation of double bond migration and succeeding rearrangements for the formation of the C5- and C7-species and various rearrangements, including a double bond, for the formation of the C6-species at high temperature. The activation energies for the pyrolysis product ratios of(C5+C6+C7)/C4 and C8/C4 were used to explain the competition reactions to form the pyrolysis products.

• Bulletin of the Korean Chemical Society
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• v.13 no.1
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• pp.59-64
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• 1992

The contrasting behaviour of meso-and d,l-$D_3$-trishomocubylidene-$D_3$-trishomocubane (1 and 2) in the electrophilic addition reaction, the former giving rearranged spiro compound (1a and 1b) and the latter giving 1,2-adduct (2a and 2b), has been explained as arising from the secondary steric effects based on computational evidence. As the degree of out-of-plane deformation of the olefinic carbon atoms increases with reaction progress, the resulting internal congestion in the region behind the double bond becomes unbearably large in meso-1. The absence of symmetry plane across the double bond of d,l-2 helps for the closing fragments to adjust themselves.

• Bulletin of the Korean Chemical Society
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• v.2 no.3
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• pp.112-114
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• 1981

The photocycloaddition reaction of 8-methoxypsoralen with purine and/or pyrimidine bases is studied as a model for the charge transfer interactions of psoralens with DNA bases by the FMO method. The results indicate that, in the case of the molecular complex formation between psoralens and purine and/or pyrimidine bases, the most probable photocycloaddition should occur in the following order: Thy (5,6)<>(3,4) 8-MOP, Cyt(5,6)<>(3,4)8-MOP, Ade (7,8)<>(3,4)8-MOP, Gua(7,8)<>(3,4)8-MOP. The theoretical results for the photocycloaddition reaction are also correlated with the experimental results. The photoadducts between 8-methoxypsoralen and adenine are likely to be C4-cycloadducts through the cycloaddition of 3,4-pyrone double bond of 8-methoxypsoralen to 7,8-double bond of adenine.

• Bulletin of the Korean Chemical Society
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• v.20 no.6
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• pp.712-714
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• 1999

The rate constants for the nucleophilic addition of potassium cyanide to α,N-diphenylnitrone and its derivatives (p-OCH3, p-CH3, p-Cl, and p-NO2) were determined by ultraviolet spectrophotometer at 25℃, and the rate equations which can be applied over a wide pH range were obtained. On the basis of pH-rate profile, adduct analysis, general base catalysis and substituent effect, a plausible mechanism of this addition reaction was proposed: At high pH, the cyanide ion to carbon-nitrogen double bond was rate controlling, however, in acidic media, the reaction proceeded by the addition of hydrogen cyanide molecule to carbon-nitrogen double bond after protonation at oxygen of a,N-diphenylnitrone. In the range of neutral pH, these two reactions occured competitively.

• Bulletin of the Korean Chemical Society
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• v.15 no.11
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• pp.957-961
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• 1994

Epoxidation of olefins catalyzed by iron-tetraarylporphyrins were studied to see the shape selectivity in the competing reaction between cis-and trans- or internal and external olefins. Cis-olefins were more reactive than trans-olefins in the competing reaction between cis-and trans-olefins. Interestingly, in the epoxidation of $cis-{\beta}-methystyrene$ by ${\alpha}{\beta}{\alpha}{\beta}$ atropisomer of Fe(III)TNPPPCl and iodosylbenzene, 27% of total product was phenylacetone. The unusually large amount of phenylacetone may be produced by hydride rearrangement of carbocationic intermediate. Regioselectivity of the reaction was also studied by using the most sterically hindered Fe(III)TTPPPCl. In the epoxidation of limonene with Fe(III)TTPPPCl, the disubstituted double bond was more reactive than trisubstituted double bond. This is in contrast to the results obtained with other iron-tetraarylporphyrins. Similar trend was also observed in the competing reaction between mono-and di-substituted olefins.

• Bulletin of the Korean Chemical Society
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• v.8 no.5
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• pp.376-380
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• 1987

The cyclobutane forming photocycloaddition reaction of 5(E)-styryl-1,3-dimethyluracil with some olefins occurs on the 5,6-double bond of uracil ring rather than the expected central double bond via an intermediate, probably the photochemical Diels-Alder type adduct. This intermediate formed on short term irradiation of 5(E)-styryl-1,3-dimethyluracil and 2,3-dimethyl-2-butene solution is converted into the $C_4$-cycloadduct on the prolonged irradiation. Quantum yield of the intermediate formation is not linear with the concentration of 2,3-dimethyl-2-butene probably due to the secondary reaction accompanied with the complex reaction kinetics. The intermediate is formed from the lowest excited singlet state.

• Bulletin of the Korean Chemical Society
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• v.8 no.4
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• pp.298-300
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• 1987

The theoretical studies on the photocycloaddition reaction of 5,7-dimethoxycoumarin and 4',5'-dihydropsoralen with thymidine were carried out as a model for photosensitizing reaction of psoralen with DNA. The results are in reasonable agreement with experimental observations. The photoadducts between dimethoxycoumarin and thymidine were predicted to be $C_{4}$-cycloadducts through the cycloaddition of 3,4-pyrone double bond of dimethoxycoumarin to 5,6 double bond of thymidine. The major photoadduct of 4',5'-dihydropsoralen with thymidine has the anti head-to-head stereochemistry.

• Bulletin of the Korean Chemical Society
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• v.12 no.3
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• pp.301-303
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• 1991

The rate constants for the nucleophilic addition of thiophenol to $\alpha$, N-diphenylnitrone and it's derivatives (p-$OCH_3$, p-Cl, p-$NO_2$) were determined from pH 3.0 to 13.0 by UV spectrophotometry and rate equations which can be applied over a wide pH range were obtained. On the basis of rate equation, general base and substituent effect a plausible addition mechanism of thiophenol to ${\alpha}$, N-diphenylnitrone was proposed: At high pH, the addition of sulfide ion to carbon-nitrogen double bond was rate controlling, however, in acidic solution, reaction was proceeded by the addition of thiophenol molecule to carbon-nitrogen double bond after protonation at oxygen of ${\alpha}$, N-diphenylnitrone.

• Bulletin of the Korean Chemical Society
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• v.3 no.4
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• pp.153-157
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• 1982

$C_4$-Photocycloaddition of 8-methoxypsoralen (8-MOP) and 5,7-dimethoxycoumarin (DMC) to maleimide was studied in order to elucidate the mechanism of the photobiological activities of these molecules. The photoreaction was carried out in chloroform solution and frozen aqueous solution state. The major product was isolated and characterized by spectroscopic methods. The photoadduct between 8-MOP and maleimide was shown to be an 1:1 $C_4$-cycloadduct through the photocycloaddition of 4',5'-furyl double bond of 8-MOP to maleimide. The stereochemistry of cyclobutane ring of this photoadduct is consistent with the anti configuration. The photoadduct between DMC and maleimide was shown to be an 1:1 $C_4$-cycloadduct through the photocycloaddition of 3,4-pyrone double bond of DMC to maleimide.

• Bulletin of the Korean Chemical Society
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• v.3 no.4
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• pp.162-165
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• 1982

The rate constants of the nucleophilic addition of thioglycolic acid to the derivatives $(H,\;p-CH_3,\;p-CH_3O,\;p-Cl,\;p-NO_2)$ of ${\beta}$-nitrostyrene were determined by ultraviolet spectrophotometry. The rate equations which can be applied over a wide pH range were obtained. Therefrom a reaction mechanism was proposed. Above pH 8.5 sulfide anion adds to the double bond (Michael type addtion). However, below pH 8.5, the neutral molecule and $HSCH_2COO^{\theta}$ add to the double bond.