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Journal of the Korean Chemical Society (JKCS)

ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 38, Number 10
JKCSEZ 38(10)
August 20, 1994 

 
Title
Kinetic Studies on the Oxidation Reaction of Malonic Acid by Ceric Ion

세륨(Ⅳ)에 의한 말론산의 산화반응에 관한 반응속도론적 연구
Author
Wang-Ki Kim

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Keywords
Abstract
1M 황산용액에서 세륨(Ⅳ) 이온에 의한 말론산의 산화반응에 관한 반응속도를 분광광도법으로 연구하였다. 말론산이 과량으로 존재하는 조건하에서 측정된 유사일차 속도상수, kobs는 말론산의 농도, [MA]에 따라 크게 의존함을 보였으며 kobs = (0.592[MA])/(1+14.5[MA]2)의 관계를 만족하였다. 이에 근거하여 반응메카니즘을 제안하였다. 말론산의 산해리에 의해 생성된 enolate형 음이온과 Ce(Ⅳ)간의 전자이동반응이 반응속도 결정단계이며, MA의 고농도하에서 Ce(Ⅳ)과 enolate형 음이온간의 1:2 chelate생성반응에 의하여 Ce(Ⅳ)의 농도가 감소하여 산화반응이 억제됨을 알 수 있었다. 본 연구에서 제안된 메카니즘에 근거하여 Sengupta 등에 의해 연구된 pH 의존성을 설명할 수 있었다.

The kinetics of the oxidation reaction of malonic acid by ceric ion in 1 M sulfuric acid solution at 20℃ have been investigated by spectrophotometric method. The reaction rate at a large excess of malonic acid was found to be pseudo-first order. The observed pseudo-first order rate constants, kobs, are dependent on the concentration of malonic acid, [MA], of which relationship has been found to be kobs = (0.592[MA])/(1+14.5[MA]2). A mechanism for the reaction has been suggested on the basis of the above rate equation. The rate determining step may be the electron transfer reaction between enolate type malonate anion, which is formed by the acid dissociation reaction of malonic acid, and Ce(Ⅳ). The rate depression in the range of high concentration of MA has been explained by the formation of 1 : 2 chelate between Ce(Ⅳ) and malonate. According to the mechanism, the pH dependence of the rate, which was studied by Sengupta et al., has also been explained.

Page
705 - 709
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