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(The) effect of added anions on the aqueous oxidation of nitrous acid by hydrogen peroxide

Title
(The) effect of added anions on the aqueous oxidation of nitrous acid by hydrogen peroxide
Authors
金蘭兮
Issue Date
1989
Department/Major
교육대학원 과학교육전공화학교육분야
Keywords
anionsaqueous oxidationnitrous acidhydrogen peroxide
Publisher
이화여자대학교 교육대학원
Degree
Master
Advisors
박종윤
Abstract
산성 수용액에서 H_(2)O_(2)에 의한 HNO_(2)의 산화 반응 (1)은 산 침적(acid deposition) 현상의 주 요인 중 하나인 HNO_(3)를 생성한다는 측면에서 중요한 반응이며, nitrosation반응의 메카니즘을 따르는 일종의 O-nitrosation반응이다. N-nitrosation과 S-nitrosation 반응에 특정 음이온이 첨가되면 촉매효과가 나타나 반응속도가 빨라짐이 보고되었으므로 반응(1)에 여러가지 음이온 (X-: CIO^(-)_(4), NO^(-)_(3), Cl^(-), Br^(-) SCN^(-))을 첨가하여 반응속도에 미치는 음이온들의 효과를 관찰하였다. 반응(1)에 ClO^(-)_(4),NO^(-)_(3)를 첨가했을 때는 이들 음이온에 의한 촉매 효과가 나타나지 않았으며, '반응 (1)의 속도식은 -d[HNO_(2)]/dt = ka_(H)[HNO_(2)] (H_(2)O_(2))임을 확인하였고, pH 2-4, 이온 세기 0.5M, 0℃에서 측정된 k값은 (1.12 ± 0.11) × 10^(3) M^(-2) s^(-1) 으로 선행 연구 결과들과 잘 일치하였다. 그러나. 반응(1)에 Cl^(-), Br^(-), SCN^(-)을 첨가했을 때는 촉매 효과를 보였고 그 크기는 SCN^(-) > Br^(-) > Cl^(-)의 순으로 관찰되었다. 이러한 효과는 음이온(X^(-))과 HNO_(2)로 부터 생성된 NOX도 nitrosating agent로 작용하는데 기인하는 것이며 NOX의 평형 농도를 고려하면 NOX의 반응성의 크기는 NOCI > NOBr > NOSCN의 순이 되며, 이결과는 N-nitrosation이나 S-nitrosation반응의 경우와 일치하였다.;The aqueous-phase oxidation of nitrous acid by hydrogen peroxide(1) has been regarded as an O-nitrosation reaction and has been considered to be important in the view of forming nitric acid that contributes much of the acid deposition phenomena. Since some anions such as C1^(-), Br^(-), and SCN^(-) have been suggested to show nucleophilic catalysis in the N-nitosation and S-nitrosation reactions, the effect of some added anions on the reaction (1), an O-nitrosation reaction has been studied at pH 2.08, 3.09,'and 3.80. No catalytic effect was found for ClO_(4)^(-) and NO_(3)^(-). The rate equation has been confirmed to be -d[HNO_(2)] / dt =ka_(H)^(+)[HNO_(2)][H_(2)O_(2)] and k determined is ( 1.12±0.11) × 10^(3) M^(-1) s^(-1) at 0℃ and ionic strength 0.5M which turns out to be consistent with those of earlier studies. The catalytic effect was found for C1^(-), Br^(-) and SCN^(-) with the order of the effect SCN^(-) > Br^(-) > C1^(-). This effect is due to the role of NOX as a nitrosating agent, which was formed in the presence of these anions from the reaction of an anion(X^(-)) with the nitrous acid. With regards to the equilibrium concentration of NOX formed, the reactivity of NOX is found to be in the order of NOCl > NOBr > NOSCN which is consistent with the results of other nitrosation reactions.
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