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RISS 인기검색어
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- 발행기관 : Korea Chemical Society (검색결과 3 건)
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N-Oxidation of Pyrazines by Bromamine-B in Perchloric Acid Medium: Kinetic and Mechanistic Approach
Puttaswamy,Shubha, J.P. Korea Chemical Society 2009 Bulletin of the Korean Chemical Society Vol.30 No.9
Kinetic investigations on the oxidation of pyrazine and four 2-substituted pyrazines viz., 2-methylpyrazine, 2-ethylpyrazine, 2-methoxypyrazine and 2-aminopyrazine by bromamine-B (BAB) to the respective N-oxides have been studied in HCl$O_4$ medium at 303 K. The reactions show identical kinetics being first-order each in $[BAB]_o\;and\;[pyrazine]_o$, and a fractional- order dependence on $[H^+]$. Effect of ionic strength of the medium and addition of benzenesulfonamide or halide ions showed no significant effect on the reaction rate. The dielectric effect is positive. The solvent isotope effect was studied using $D_2$O. The reaction has been studied at different temperatures and activation parameters for the composite reaction have been evaluated from the Arrhenius plots. The reaction showed 1:1 stoichiometry and the oxidation products of pyrazines were characterized as their respective N-oxides. Under comparable experimental conditions, the oxidation rate of pyrazines increased in the order: 2-aminopyrazine > 2-methoxypyrazine > 2-ethylpyrazine > 2-methylpyrazine > pyrazine. The rates correlate with the Hammett $\sigma$ relationship and the reaction constant $\rho$ was found to be -0.8, indicating that electron donating centres enhance the rate of reaction. An isokinetic temperature of $\beta$ = 333 K, indicated that the reaction was enthalpy controlled. A mechanism consistent with the experimental results has been proposed in which the rate determining step is the formation of an intermediate complex between the substrate and the diprotonated species of the oxidant. The related rate law in consistent with observed results has been deduced.
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Saravanan, V.,Shivakumar, R.,babu, P. Niruguna,Ramakrishna Korea Chemical Society 2009 대한화학회지 Vol.53 No.6
여러 $CO_2-O_2$ 혼합기체에서 인도산 분말숯의 연소반응실험을 수행하였다. 샘플을 분쇄하여 58 마이크론보다 작은 채로 거르고 질소분위기에서 숯으로 만들었다. CPRI 방갈로에 있는 열분석기 (TGA-50)을 사용해 실험을 하였다. $CO_2-O_2$ 혼합기체는 몰비로 (80-20, 60-40, 40-60, 20-80)을 사용하였다. 활성화에너지 (E) 및 지수앞자리인자 (A)을 통합접근 및 수정된 Arrhenius식을 사용해 계산하였다. Experimental work was carried out to study the combustion kinetics of the Indian coal-char in the varying mixture of carbon dioxide-oxygen ($CO_2-O_2$). The coal sample was pulverized and sieved to less than 58 microns and charred using volatile furnace by passing the nitrogen gas. The experiments were carried out using the Thermo Gravimetric Analyzer (TGA-50) at CPRI, Bangalore, different proportions of ($CO_2-O_2$) gas was allowed in to the TGA-50 (80-20, 60-40, 40-60, 20-80) mole basis were used to study the combustion kinetics of coal Isothermally, kinetic parameters like Activation energy (E) and the pre-exponential factors (A) are calculated using the unification approach and modified Arrhenius equation.
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