• 제목/요약/키워드: Oxidation reaction pathway

검색결과 37건 처리시간 0.019초

광펜톤 반응에 의한 수중 2-클로로페놀 분해특성연구 (Degradation of 2-Chlorophenol in the Aqueous Phase by a Photo-Fenton Process)

  • 김일규
    • 상하수도학회지
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    • 제26권6호
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    • pp.779-786
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    • 2012
  • The degradation of 2-chlorophenol(2-CP) by various AOPs(Advanced Oxidation Processes) including the photo-Fenton process has been examined. In sole $Fe^{2+}$, UV or $H_2O_2$ process without combination, low removal efficiencies have been achieved. But the photo-Fenton process showed higher removal efficiency for degradation of 2-chlorophenol than those of other AOPs including the Fenton process and the UV processes. In the photo-Fenton process, the optimal experimental conditions of 2-chlorophenol degradation were obtained at pH 3 and the $Fe^{2+}/H_2O_2$molar ratio of 1. Also the 2-chlorophenol removal efficiency increased with decreasing of the initial 2-chlorophenol concentration. 3-chlorocatechol and chlorohydroquinone were identified as photo-Fenton reaction intermediates, and a degradation pathway of 2-chlorophenol in the aqueous phase during the photo-Fenton reaction was proposed.

Sonochemical Reaction Mechanism of a Polycyclic Aromatic Sulfur Hydrocarbon in Aqueous Phase

  • Kim, Il-Kyu;Jung, Oh-Jin
    • Bulletin of the Korean Chemical Society
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    • 제23권7호
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    • pp.990-994
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    • 2002
  • Hydroxybenzothiophenes, dihydroxy-benzothiophenes, and benzothiophenedione were identified as inter-mediates of benzothiophene (BT) exposed to ultrasonic irradiation. It is proposed that benzothiophene is oxidized by OH radical to sequentially for m hydroxybenzothiophenes, dihydroxybenzothiophenes, and benzothiophenedione. Benzothiophene is decomposed rapidly following pseudo-first-order kinetics in a first-order manner by ultrasonic irradiation in aqueous solution. The toxicity of sonochemically treated solutions was checked by E. coli and a less inhibition in bacterial respiration was observed from the 120-min treated benzothiophene sample than from the untreated benzothiophene sample. Also evolution of carbon dioxide and sulfite was observed during ultrasonic reaction. A pathway for ultrasonic decomposition of benzothiophene in aqueous solution is proposed.

Kinetics of Oxidation of Nitrotoluenes by Acidic Hexacyanoferrate (Ⅲ)

  • Bhattacharjee, A. K.;Mahanti, M. K.
    • Bulletin of the Korean Chemical Society
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    • 제4권3호
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    • pp.120-123
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    • 1983
  • The reaction of hexacyanoferrate (Ⅲ) with nitrotoluenes in aqueous acetic acid containing perchloric acid(1.0 M) at $50^{\circ}C$ gave the corresponding aldehyde as the major product. The order with respect to each of the reactants ― substrate, oxidant and acid ― was found to be unity. The Hammett plot yielded a ${\sigma}^+$ value of -1.30, and the kinetic isotope effect gave a $k_H/k_D$ value of 6.2. The pathway for the conversion of the nitrotoluenes to the products has been mechanistically visualized as proceeding through the benzylic radical intermediate, formed in the rate determining step of the reaction.

Effect of Cobalt Loading on the Performance and Stability of Oxygen Reduction and Evolution Reactions in Rechargeable Zinc-air Batteries

  • Sheraz Ahmed;Joongpyo Shim;Gyungse Park
    • 대한화학회지
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    • 제68권2호
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    • pp.87-92
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    • 2024
  • The commercialization of rechargeable metal-air batteries is extremely desirable but designing stable oxygen reduction reaction (ORR) catalysts with non-noble metal still has faced challenges to replace platinum-based catalysts. The nonnoble metal catalysts for ORR were prepared to improve the catalytic performance and stability by the thermal decomposition of ZIF-8 with optimum cobalt loading. The porous carbon was obtained by the calcination of ZIF-8 and different loading amounts of Co nanoparticles were anchored onto porous carbon forming a Co/PC catalyst. Co/PC composite shows a significant increase in the ORR value of current and stability (500 h) due to the good electronic conductive PCN support and optimum cobalt metal loading. The significantly improved catalytic performance is ascribed to the chemical structure, synergistic effects, porous carbon networks, and rich active sites. This method develops a new pathway for a highly active and advantageous catalyst for electrochemical devices.

Intramolecular Ion-Molecule Reactions within Ti+(CH3COCH3)n Heteroclusters: Oxidation Pathway via C=O Bond Activation

  • Koo, Young-Mi;Hong, Ki-Ryong;Kim, Tae-Kyu;Jung, Kwang-Woo
    • Bulletin of the Korean Chemical Society
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    • 제31권4호
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    • pp.953-958
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    • 2010
  • A laser ablation-molecular beam/reflectron time-of-flight mass spectrometric technique was used to investigate the ion-molecule reactions that proceed within $Ti^+(CH_3COCH_3)_n$ heterocluster ions. The reactions of $Ti^+$ with $CH_3COCH_3$ clusters were found to be dominated exclusively by an oxidation reaction, which produced $TiO^+(CH_3COCH_3)_n$ clusters. These ions were attributed to the insertion of a $Ti^+$ ion into the C=O bond of the acetone molecule within the heteroclusters, followed by $C_3H_6$ elimination. The mass spectra also indicated the formation of minor sequences of heterocluster ions with the formulas $Ti^+(C_3H_4O)(CH_3COCH_3)_n$ and $TiO^+(OH)(CH_3COCH_3)_n$, which could be attributed to C-H bond insertion followed by $H_2$ elimination and to the sequential OH abstraction by the $TiO^+$ ion, respectively. Density functional theory calculations were carried out to model the structures and binding energies of both the association complexes and the relevant reaction products. The reaction pathways and energetics of the $TiO^+\;+\;CH_2CHCH_3$ product channel are presented.

DFT/B3LYP Study of the Substituent Effects on the Reaction Enthalpies of the Antioxidant Mechanisms of Magnolol Derivatives in the Gas-Phase and Water

  • Najafi, Meysam;Najafi, Mohammad;Najafi, Houshang
    • Bulletin of the Korean Chemical Society
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    • 제33권11호
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    • pp.3607-3617
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    • 2012
  • In this paper, the study of various ortho- and meta-substituted Magnolol derivatives is presented. The reaction enthalpies related to three antioxidant action mechanisms HAT, SET-PT and SPLET for substituted Magnolols have been calculated using DFT/B3LYP method in gas-phase and water. Calculated results show that electron-withdrawing substituents increase the bond dissociation enthalpy (BDE), ionization potential (IP) and oxidation/reduction enthalpy (O/RE), while electron-donating ones cause a rise in the proton dissociation enthalpy (PDE) and proton affinity (PA). In ortho- position, substituents show larger effect on reaction enthalpies than in meta-position. In comparison to gas-phase, water attenuates the substituent effect on all reaction enthalpies. In gas-phase, BDEs are lower than PAs and IPs, i.e. HAT represents the thermodynamically preferred pathway. On the other hand, SPLET mechanism represents the thermodynamically favored process in water. Results show that calculated enthalpies can be successfully correlated with Hammett constants (${\sigma}_m$) of the substituted Magnolols. Furthermore, calculated IP and PA values for substituted Magnolols show linear dependence on the energy of the highest occupied molecular orbital ($E_{HOMO}$).

Ferrate(VI)를 이용한 다양한 수중 환경에서의 tetracycline의 분해 특성 및 반응 경로 연구 (Degradation characteristics and reaction pathways of tetracycline by ferrate(VI) in various aqueous conditions)

  • 박경덕;김일규
    • 상하수도학회지
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    • 제35권1호
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    • pp.27-37
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    • 2021
  • Tetracycline is one of the most commonly used as antibiotics for the livestock industry and it is still widely used nowadays. Tetracycline and its metabolites are excreted with excrement, which is difficult to completely removed with conventional sewage treatment, therefore it is apprehended that the tetracycline-resistant bacteria occurs. In this study, the oxidant named ferrate(VI) was used to degrade the tetracycline and investigate the reaction between ferrate(VI) and tetracycline under various aqueous conditions. The highest degradation efficiency of tetracycline occurred in basic condition (pH 10.1 ± 0.1) because of the pKa values of tetracycline and ferrate(VI). The results also showed the effect of water temperature on the degradation of tetracycline was not significant. In addition, the dosage of ferrate(VI) was higher, the degradation of tetracycline and the self-degradation of ferrate(VI) also higher, finally the efficiency of ferrate(VI) was lower. The results said that the various mechanisms effects the reaction of ferrate(VI) oxidation, it required the consideration of the characteristics of the target compound for optimal degradation efficiency. Additionally, intermediate products were detected with LC/MS/MS and three degradation pathways were proposed.

Bruceantin 유사체의 전합성에 대한 연구 (Ⅰ) (Study for Total Synthesis of Bruceantin Analogue(Ⅰ))

  • 주정호;최정진;김홍범
    • 대한화학회지
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    • 제38권1호
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    • pp.80-86
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    • 1994
  • Bruceantin유사체 전합성의 중요한 중간체인 ethyl $({\pm})$-8-oxo-10-oxa-l'H-spiro[1, 3]dioxolane-4,4'-tricyclo [9.2.1.0 1,6]dodec-6-ene-9-carboxylate (7)의 합성경로를 개발하였다. 시작물질로서 ethyl 2-cyclohexanonecarboxylate and methyl vinyl ketone을 사용하여, Robinson annulation, allylic oxidation등을 응용하였으며, regiospecific acylation and the formation of epoxy methano bridge 형성 반응 등이 연구되었다. Actalone (3)의 ketalization 반응에서 새로운 decarboethoxylation 반응을 발견하였으며, 이 반응을 이용하여 3차 알코올과 엔온을 가지고 있는 4,4a,5,6,7,8-Hexahydro-4a-hydroxy-2(3H)naphthalenone (14)를 합성하였다.

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칠피(漆皮) 부탄올 분획물이 LPS로 유도된 RAW 264.7 대식세포에 미치는 영향 (Effects of Butanol extract from Rhois Vernicifluae Cortex (RVC) in lipopolysaccharides-induced macrophage RAW 264.7 cells)

  • 송생엽;심성용;김경준
    • 한방안이비인후피부과학회지
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    • 제20권1호통권32호
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    • pp.1-15
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    • 2007
  • Objectives : RVC has long been used for a useful natural agent ameliorating inflammation related symptoms in the folk medicine recipe. This study was performed to investigate effects of RVC on the inflammation and oxidation in RAW 264.7 cells. Methods : The RVC was extracted with 80% ethanol and sequentially partitioned with solvents in order to increase polarity. With the various fractions, we determined the activities on the inflammation and oxidation in RAW 264.7 cells. Results : 1. Among the various solvent extracts of RVC, the butanol fraction showed the most powerful inhibitory ability against nitric oxide (NO) production in lipopolysaccharide (LPS)-induced RAW 264.7 cells without affecting cell viability. 2. Butanol fraction showed a oxidation inhibition effect by decreasing the DPPH and OH radicals. 3. Butanol fraction exhibited the inhibitory avilities against iNOS and COX-2. 4. Reverse transcriptase polymerase chain reaction (RT-PCR) and Westem blotting analysis revealed that the BuOH fraction provided a primary inhibitor of the iNOS protein and mRNA expression in LPS-induced RAW 264.7 cells. Among the up-regulater molecules of iNOS and COX-2, the BuOh fraction of RVC was shown the inhibitory activity of phoshporylation of c-Jun N-terminal kinase (JNK) 1/2 and threonine protein kinase (AKT), the one of the MAPKs pathway. Conclusion : Thus, the present study suggests that the response of a component of the BuOH fraction to NO generation via iNOS expression provide a important clue to elucidate anti-inflammatory and anti-oxidation mechanism of RVC.

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초음파조사에 의한 염화불화탄소(CFC)의 분해 (Decomposition of Chlorofluorocarbon by Sonication)

  • 임봉빈;김선태
    • 한국대기환경학회지
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    • 제19권3호
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    • pp.307-314
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    • 2003
  • The sonolytic decomposition of chlorofluorocarbon (CFC 113) and several alternative compounds, such as HCFC 225ca, HCFC 225cb, and HFC 134a, in.aqueous solutions was investigated. The CFC 113 with a high volatility and a low solubility in water was rapidly decomposed with increasing sonication time. The decomposition rates were influenced by the initial concentration of CFC 113, the reaction temperature, and the gas/liquid phase volume ratio but were independant of the pH of solution. The predominant pathway of the decomposition of CFC 113 by sonication was not the oxidation by OH radicals but the pyrolysis with high temperature and pressure inside of the cavitation bubble. The pyrolysis in the cavitation bubble resulted in an almost complete mineralization of CFC 113 with the high efficient formation of inorganic products (Cl$^{[-10]}$ , F$^{[-10]}$ , CO, $CO_2$). The addition of zinc powder on the decomposition of CFC 113 by sonication caused an acceleration of the decomposition. Also, HCFCs and HFC 134a were found to be readily decomposed by the pyrolysis induced from the sonication.