• Bulletin of the Korean Chemical Society
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• v.34 no.12
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• pp.3738-3742
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• 2013

The reaction mechanism of $SiF_2$ radical with HNCO has been investigated by the B3LYP method of density functional theory(DFT), while the geometries and harmonic vibration frequencies of reactants, intermediates, transition states and products have been calculated at the B3LYP/$6-311++G^{**}$ level. To obtain more precise energy result, stationary point energies were calculated at the CCSD(T)/$6-311++G^{**}$//B3LYP/$6-311++G^{**}$ level. $SiF_2+HNCO{\rightarrow}IM3{\rightarrow}TS5{\rightarrow}IM4{\rightarrow}TS6{\rightarrow}OSiF_2CNH(P3)$ was the main channel with low potential energy, $OSiF_2CNH$ was the main product. The analyses for the combining interaction between $SiF_2$ radical and HNCO with the atom-in-molecules theory (AIM) have been performed.

• Toxicological Research
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• v.18 no.2
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• pp.159-165
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• 2002

Recently, we reported (korean J. Biomed. Lab. Sci., 6(4): 245-251, 2000) that cyclohexane (l.56 g/kg of body wt., i.p.) administration led to lung injury in rats. However the detailed mechanism remain to be elucidated. This study was designed to clarify the mechanism of lung damage induced by cyclohexane in rats. First, lung damage was assessed by quantifying bronchoalveolar lavage fluid (BAL) protein content as well us by histopathological examination. Second, activities of serum xanthine oxidase (XO), pulmonary XO and oxygen free radical scavenging enzymes. XO tope conversion (O/D + O, %) ratio and content of reduced glutathione (GSH) were determined. In the histopathological findings, the vasodilation, local edema and hemorrhage were demonstrated in alveoli of lung. And vascular lumens filled with lipid droplets, increased macrophages in luminal margin and increased fibroblast-like interstitial cells in interstitial space were observed in electron micrographs. The introperitoneal treatment of cyclohexane dramatically increased BAL protein by 21-fold compared with control. Cyclohexane administration to rats led to a significant rise of serum and pulmonary XO activities and O/D + O ratio by 47%,30% and 24%, respectively, compared witれ control. Furthermore, activities of pulmonary oxygen free radical scavenging enzymes such as superoxide dismutase, glutathione peroxidase and glutathione S-transferase, and GSH content were not found to be statistically different between control and cyclohexane-treated rats. These results indicate that intraperitoneal injection of cyclohexane to rats may induce the lipid embolism in pulmonary blood vessel and lead to the hypoxia with the ensuing of oxygen free radical generation, and which may be responsible for the pulmonary injury.

• Preventive Nutrition and Food Science
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• v.3 no.1
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• pp.48-55
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• 1998

An acute ethanol load(50mmol/kg , i.p) resulted in an increase in peroxidation and a decrease in the levels of $\alpha$-tocopherol and ascorbate in rat cerebellum. Pretreatement with allopurinol(146$\mu$mol/kg, i.p) prevented the ethnol-induced increment in lipid peroxidation and decrease in $\alpha$-tocopherol content. However, the decrease of ascorbate was of greater magnitude when allopurinol was associated with ethanol. These results suggested that allopurinol. besides its action as a radical scavenger and xanthine oxidase inhibitor, might favor the regeneration of $\alpha$-tocopherol antioxidant acitviity was studied using ${\gamma}$-radiolysis in aerated ethanolic solutions. Even though allopurinol did not react by itself with $\alpha$-hydroxyethyl-peroxyl radicals [H3C-CH(OH)OO] , it enhance the $\alpha$-hydroxyethyl-peroxyl radical scavenging properties of $\alpha$tocopherol. The regeneration of $\alpha$-tocopherol from the $\alpha$-hydroxyethyl-peroxyl radical scavenging properties of $\alpha$-tocophero. The regeneration of $\alpha$-tocopherol from the $\alpha$-tocopherol radical by ascorbate remained as efficient in the presence of allopurinol as in its absence. The effects of allopurinol on the Vitamin E oxidation-reduction mechanism could be involoved in the beneficial effectof allopurinol on the biological cellular damages linked to free radical reactions.

• Bulletin of the Korean Chemical Society
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• v.10 no.4
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• pp.374-377
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• 1989

Photolysis of dichlorodiphenylmethane in glassy 2-MeTHF at 77K results in the formation of diphenylcarbene and the diphenylchloromethyl radical, which were detected by their flourescence emission and excitation spectra. The relative yield of the carbene to radical is shown to vary dramatically as a function of irradiation time. The photolability of the radical is also demonstated. These results were interpreted in terms of a two step mechanism, where the diphenylchloromethyl radical is an intermediate in the formation of diphenylcarbene.

• The Korean Journal of Food And Nutrition
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• v.10 no.1
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• pp.6-13
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• 1997

Reactivity and reaction mechanism for the photosensitized generation of hydroxyl radical by various coumarin derivatives are investigated by means of ESR and laser flash photolysis methods. The nine kinds of coumarin derivatives show to be proceeded through the OH·radical generation mechanism, however 1-ethyl-3-nitro-1-nitrosoguanidine decomposes and produces the carbene intermediate before OH·radical generation reaction occurs. The nine coumarin derivatives show the signals, which are corresponded to DMPO-OH spin adducts. NaN3, EtOH and HCOONa act as a strong photosensitizer to quench OH·radical. The decay rate constants of the hydrated electrons in the case of added N2O show higher than added K3Fe(CN)6.

• Journal of the Korean Electrochemical Society
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• v.12 no.1
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• pp.54-60
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• 2009

The redox characteristics of 2-arylaldehydehydrazono-3-phenyl-5-substituted-2, 3-dihydro-1, 3, 4-thiadiazoles (1a-h) have been investigated in nonaqueous solvents such as 1, 2-dichloroethane (DCE), dichloromethane (DCM), acetonitrile (AN), Tetrahydrofuran (THF), and dimethylsulfoxide (DMSO) at platinum electrode. Through controlled potential electrolysis, the oxidation and reduction products of the investigated compounds had been separated and indentified. The redox mechanism had been suggested and proved. It had been found that all the investigated compounds were oxidized in two irreversible one-electron processes following the well-known pattern of The EC-mechanism; the first electron loss gives the corresponding cation-radical which is followed by proton removal from the ortho-position in the N-phenyl ring forming the radical. The obtained radical undergoes a second electron uptake from the nitrogen in the N = C group forming the unstable intermediate (di-radical cation) which undergoes ring closure forming the corresponding cation. The formed cation was stabilized in solution through its combination with a perchlorate anion from the medium. On the other hand, these compounds are reduced in a single two-electron process or in a successive two one-electron processes following the well known pattern of the EEC-mechanism according to the nature of the substituent; the first one gives the anion-radical followed by a second electron reduction to give the dianion which is basic enough to abstract protons from the media to saturate the (C = O) bond.

• Journal of the Korean Society of Combustion
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• v.4 no.1
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• pp.39-47
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• 1999

A combustion flame visualization system, which is used as an engine diagnostics tool, was developed in order to understand the combustion reaction mechanism in the development stage for S.I. engines. The measurement system consists of an I-CCD camera and a computer-aided image processing system. By using optically accessible engine system, the flame structure was analyzed from the acquired graylevel image and the direction of flame propagation (shape of flame) has been measured to understand combustion phenomena. And combustion radical which involves combustion information were measured. As a result, strong relation between combustion radicals intensity ratio and air excess ratio was found.

• Journal of the East Asian Society of Dietary Life
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• v.3 no.2
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• pp.121-128
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• 1993

This study was intended to clarify the protective mechanism of diallyl disulfide on the carbon tetrachloride-induced hepatotoxicity in mice. It was observed that a powerfully increment of serum alanine aminotransferase activity and hepatic lipid peroxide content after carbon tetrachloride injection were markedly inhibited by the pretreatment of diallyl disulfide (20mg/kg) for 5 days. It was also observed that hepatic aminopyrine demethylase and xanthine ocidase as free radical generating enzymes as well as superoxide dismutase and catalase activities as free frdical scavenging enzymes and hepatic glutathione content were not changed by the pretreatment with diallyl disulfide. But, treatment with diallyl disulfide did signifiantly increase cytosolic glutathione S-transferase activity. However, glutathione S-transferase activity in the presence of diallyl disulfide was not affected in vitro. Therefore, it is concluded that mechanism for the observed preventive effect ofdiallyl disulfide against the carbon tetrachloride-induced hepatotoxicity can be due to the engancement of glutathione S-transferase activity.

• Environmental Analysis Health and Toxicology
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• v.18 no.3
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• pp.165-174
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• 2003

Cr (Ⅵ) - containing compounds are well-established carcinogens, although the mechanism for chromium - induced carcinogenesis is still not well understood. The reduction of Cr (Ⅵ) to its lower oxidation states, par ticularly Cr (V) and Cr (IV), is an important step for the production of chromium-mediated reactive oxygen species (ROS). The persistent oxidative stress during the reduction process may play a key role in the mechanism of Cr (Ⅵ) -induced carcinogenesis. This paper summarizes recent studies on (1) the reduction of Cr (Ⅵ) to Cr (III) occur by a multiplicity of mechanisms depending on the nature of reducing agents including ascorbate, diol-and thiol-containing molecules, certain flavoenzymes, cell organelles, intact cells, and whole animals; (2) free-radical production with emphasis on hydroxy radical generation via Fenton or Haber-Weiss type reactions; and (3) free radical - induced cellular damage, such at DNA strand breaks, hydroxylation of 2'-deoxyguanosine, and activation of nuclear transcription factor kB.

• Journal of Adhesion and Interface
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• v.2 no.2
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• pp.11-19
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• 2001

The phase-transfer catalyzed radical polymerization of styrene was carried out using tricaprylylmethylammonium chloride as a phase-transfer catalyst in a two-phase system of an aqueous $Na_2S_2O_8$ solution and toluene at $60^{\circ}C$ under nitrogen atmosphere. The initial rate of radical polymerization was expressed as the combined terms of concentrations of quaternary onium cation and peroxydisulfate anion in the aqueous phase rather than the fed concentrations of catalyst and $Na_2S_2O_8$. The observed initial rate of radical polymerization was used to analyze the radical polymerization mechanism with a cycle phase-transfer initiation step in the heterogeneous liquid-liquid system. The viscosity average molecular weight of polystyrene was inversely proportional to concentration of $Na_2S_2O_8$ expressed as $[Q^+]([S_2O{_8}^{2-}]{\alpha}_2)^{1/2}$ derived by the radical polymerization mechanism.