• Title/Summary/Keyword: Chemical reaction kinetics

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Photoinduced Electron Transfer From Aromatic Amines to Triplet States of $C_{60}$

  • Yahata, Yukio;Sasaki, Yoshiko;Fujitsuka, Mamoru;Ito, Osamu
    • Journal of Photoscience
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    • v.6 no.3
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    • pp.117-121
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    • 1999
  • Photoinduced electron transfer of C60 has been studied by the laser photolysis measuring the transient absorption bands in near-IR region. The electron transfer aromatic amines via the triplet state of C60 is confirmed by the decay of the transient absorption bands of the triplet state of C60 and the rise of the anion radical of C60 and the cation radicals of amines. The rate and efficiency of electron transfer are strongly affected by the donor ability of amines and polarity of solvents. Back electron-transfer kinetics is also strongly affected by the solvent polarity.

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Kinetics on the Reaction of 3,5-Diaryl-1,2,4-dithiazolium Triodide with Hydrazine (삼요오드화 3,5-디아릴-1,2,4-디지아졸륨과 히드라진과의 반응에 관한 반응속도론적 연구)

  • Moon-Hwan Park;Chang-Suk Kim;Soon-Yung Hong
    • Journal of the Korean Chemical Society
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    • v.29 no.4
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    • pp.448-451
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    • 1985
  • Pseudo first-order rate constants for reactions of seven m- or p- phenyl-ring substituted 3,5-diphenyl 1,2,4-dithiazolium triodides with hydrazine in excess, in pyridine, were determined by a UV spectrophotometry. For these reactions, calculated some activation parameters, identified the reaction products, and investigated the effect of substituent on the reaction rate. These reactions were accelerated by electron-withdrawing substituents and obeyed the Hammett rule. From the observed kinetics, a reaction mechanism was proposed.

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Kinetics Study of Malachite Green Fading in the Presence of TX-100, DTAB and SDS

  • Samiey, Babak;Toosi, Ali Raoof
    • Bulletin of the Korean Chemical Society
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    • v.30 no.9
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    • pp.2051-2056
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    • 2009
  • The rate constants of alkaline fading of malachite green ($MG^+$) was measured in the presence of nonionic (TX-100), cationic (DTAB) and anionic (SDS) surfactants. This reaction was studied under pseudo-first-order conditions at 283∼303 K. The rate of fading reaction showed noticeable dependence on the electrical charge of the used surfactants. It was observed that the reaction rate constants were increased in the presence of TX-100 and DTAB and decreased in the presence of SDS. According to Hughs-Ingold rules for nucleophilic substitution reactions, the electric charge of MG/surfactant compound along with decrease in dielectric constant of $MG^+$ micro-environment in this compound varies the rate of fading reaction. Binding constants of surfactant molecules to $MG^+$ were calculated using cooperativity, pseudo-phase ion exchange and classical models and the related thermodynamic parameters were obtained by classical model. The results show that the binding of $MG^+$ to TX-100 is exothermic and binding of $MG^+$ to DTAB and SDS in some concentration ranges of the used surfactants is endothermic and in the other ones is exothermic.

Kinetics of the Reaction of Benzyl Bromides with Thiourea (Benzyl Bromide 類와 Thiourea의 反應에 關한 反應速度論的 硏究)

  • Yoh, Soo-Dong;Lee, Dae-Soo;Hong, Soon-Yung
    • Journal of the Korean Chemical Society
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    • v.13 no.3
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    • pp.215-219
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    • 1969
  • The kinetics of the reaction of m-or p-substituted benzyl bromides with thiourea in methanol at 35.0$^{\circ}$were determined by an electric conductivity method. According to a plot of log k against the Hammett substituent constants, C-Br bond cleavage in benzyl bromide is postulated to be a rate determining step at the SN2 reaction of benzyl bromide with thiourea. Both electron-donating substituents and electron-withdrawing substituents quantitatively affected the rate of reaction, but each in a different manner. A mechanistic possibility was proposed to account for the results. Some activation parameters were also calculated.

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Cure Kinetics of DGEBA/MDA/SN/HQ Thermosetting Matrix (열경화성 DGEBA/MDA/SN/HQ 매트릭스의 경화반응 속도)

  • Lee, Jae-Yeong;Sim, Mi-Ja;Kim, Sang-Uk
    • Korean Journal of Materials Research
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    • v.5 no.6
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    • pp.667-672
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    • 1995
  • Cure kinetics of DGEBA(diglycidyl ether of bisphenol A)/MDA(4, 4'-methylene dianiline)/SN(succinonitrile) system and DGEBA/MDA/SN/HQ(hydroquinone) system was studied by Kissinger equation and Fractional life method through DSC in the temperature range of 85∼150$^{\circ}C$. As cure temperature was increased, reaction rate increased and reaction order was almost constant. The reaction rate of the system with HQ as a catalyst was more higher and activation energy of that was lower about 20% than those of the system without HQ. Starting temperature of cure reaction for DGEBA/MDA/SN/HQ system decreased about 30$^{\circ}C$ than that of DGEBA/MDA/SN system.

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Kinetic Studies on Bromine-Exchange Reactions of Antimony Tribromide with $\alpha$-Phenyl-n-butyl and $\alpha$-Phenyl-i-butyl Bromides in Nitrobenzene$^\dag$

  • Rhyu, Sok-Hwan;Choi, Sang-Up
    • Bulletin of the Korean Chemical Society
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    • v.8 no.5
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    • pp.408-414
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    • 1987
  • The rate of bromine-exchange reaction between antimony tribromide and ${\alpha}-phenyl-n-butyl$ bromide in nitrobenzene has been determined, using antimony tribromide labelled with Br-82. The results indicate that the exchange reaction follows the first-order kinetics with respect to the organic bromide, and either the second- or first-order kinetics with respect to antimony tribromide depending on its concentration. The third-order rate constant obtained was 7.50 ${\times}10^{-2}l^2mol^{-2}s^{-1}$ at 28$^{\circ}$C. Similar study on the bromine-exchange reaction between antimony tribromide and ${\alpha}$-phenyl-i-butyl bromide has also been carried out. The results of the study show the same kinetic orders as the ones observed with $\alpha$-phenyl-n-butyl bromide. The third-order rate constant observed was 2.40 ${\times} 10^{-2} l^2mol^{-2}s^{-1}$ at 28$^{\circ}$C. The activation energy, the enthalpy of activation and the entropy of activation for the two exchange reactions mentioned above have been determined. The reaction mechanisms for the exchange reactions are discussed.

Assessment of Methane Potential in Hydro-thermal Carbonization reaction of Organic Sludge Using Parallel First Order Kinetics (병열 1차 반응속도식을 이용한 유기성 슬러지 수열탄화 반응온도별 메탄생산퍼텐셜 평가)

  • Oh, Seung-Yong;Yoon, Young-Man
    • Korean Journal of Environmental Agriculture
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    • v.35 no.2
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    • pp.128-136
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    • 2016
  • BACKGROUND: Hydrothermal carbonization reaction is the thermo-chemical energy conversion technology for producing the solid fuel of high carbon density from organic wastes. The hydrothermal carbonization reaction is accompanied by the thermal hydrolysis reaction which converse particulate organic matters to soluble forms (hydro-thermal hydrolysate). Recently, hydrothermal carbonization is adopted as a pre-treatment technology to improve anaerobic digestion efficiency. This research was carried out to assess the effects of hydro-thermal reaction temperature on the methane potential and anaerobic biodegradability in the thermal hydrolysate of organic sludge generating from the wastewater treatment plant of poultry slaughterhouse .METHODS AND RESULTS: Wastewater treatment sludge cake of poultry slaughterhouse was treated in the different hydro-thermal reaction temperature of 170, 180, 190, 200, and 220℃. Theoretical and experimental methane potential for each hydro-thermal hydrolysate were measured. Then, the organic substance fractions of hydro-thermal hydrolysate were characterized by the optimization of the parallel first order kinetics model. The increase of hydro-thermal reaction temperature from 170℃ to 220℃ caused the enhancement of hydrolysis efficiency. And the methane potential showed the maximum value of 0.381 Nm3 kg-1-VSadded in the hydro-thermal reaction temperature of 190℃. Biodegradable volatile solid(VSB) content have accounted for 66.41% in 170℃, 72.70% in 180℃, 79.78% in 190℃, 67.05% in 200℃, and 70.31% in 220℃, respectively. The persistent VS content increased with hydro-thermal reaction temperature, which occupied 0.18% for 170℃, 2.96% for 180℃, 6.32% for 190℃, 17.52% for 200℃, and 20.55% for 220℃.CONCLUSION: Biodegradable volatile solid showed the highest amount in the hydro-thermal reaction temperature of 190℃, and then, the optimum hydro-thermal reaction temperature for organic sludge was assessed as 190℃ in the aspect of the methane production. The rise of hydro-thermal reaction temperature caused increase of persistent organic matter content.

Contribution of Hydrophobic Interactions to HubWA Folding Reaction (소수성 상호작용이 HubWA 단백질의 폴딩 반응에 끼치는 영향)

  • Park, Soon-Ho
    • Journal of the Korean Chemical Society
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    • v.63 no.6
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    • pp.427-434
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    • 2019
  • The role of hydrophobic residues on protein folding reaction was studied by folding kinetics measurements in conjunction with protein engineering. The HubWA, which was derived from human ubiquitin by mutating the residues at 45 (Phe to Trp) and 26 (Val to Ala), was used as a mutational background. Fourteen hydrophobic residues were mutated to alanine. Among fourteen variants generated, only four variant proteins (V5A, I13A, V17A, and I36A) were suitable for folding study. The folding kinetics of these variants was measured by stopped-flow fluorescence spectroscopy. The folding kinetics of HubWA and V17A was observed to follow a three-state on-pathway mechanism. On the other hand, folding kinetics of V5A, I13A, and I36A was observed to follow a two-state mechanism. Based on these observations, transition of protein folding reaction from collision-diffusion mechanism to nucleation-condensation mechanism was discussed.