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首页> 外文期刊>Journal of the Indian Chemical Society >Linear free energy relation in Mn~(II) catalyzed oxidation of some alpha-amino acids by Ce~(IV) - Kinetics and mechanism
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Linear free energy relation in Mn~(II) catalyzed oxidation of some alpha-amino acids by Ce~(IV) - Kinetics and mechanism

机译:Mn〜(II)催化Ce〜(IV)氧化某些α-氨基酸的线性自由能关系-动力学和机理

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摘要

Oxidation of alpha-amino acids (phenylalanine,glycine,alanine,valine,nor-lencine and iso-leucine) by Cc~(IV) is catalyzed by Mn~(II) in sulfuric acid-water medium and gave aldehyde.All these reactions arc first order with respect to amino acid,oxidant,catalyst and inverse second order with respect to H~+.Rate increases with increase in [HSO_4~-] at constant [H~+] but decreases with [H~+ ] at constant [HSO_4~-].Active species in this oxidation suggested is [Cc(SO_4)]~(2+).Mn~(II) is first oxidized to Mn~(III),which act as oxidant for the substrate.Thermodynamic parameters for rate determining step have been evaluated.Formation of cyclic intermediate and free radical mechanism involving C-C fission have been suggested.Linear Free Energy Relationship is satisfied.Reaction constant rho = +1.313,suggesting involvement of formation of electron-deficient species in the reaction.The reactivity decreased as carbon chain length increased and the observed order is phenylalanine > glycine > alanine> valine > nor-leucine > iso-leucine.
机译:Mn〜(II)在硫酸-水介质中催化Cc〜(IV)氧化α-氨基酸(苯丙氨酸,甘氨酸,丙氨酸,缬氨酸,正亮氨酸和异亮氨酸)并生成醛。相对于氨基酸,氧化剂,催化剂为一阶,相对于H〜+呈反二阶。速率随[HSO_4〜-]的增加而恒定[H〜+],但随着[H〜+]的减少而恒定[HSO_4〜-]。建议的该氧化反应中的活性物质为[Cc(SO_4)]〜(2 +)。Mn〜(II)首先被氧化为Mn〜(III),作为底物的氧化剂。热力学参数提出了确定速率的步骤,并提出了涉及CC裂变的环状中间体和自由基机理的形成。满足了线性自由能关系。反应常数rho = +1.313,表明该反应中缺乏电子物种的形成。反应性随碳链长度的增加而降低,并且观察到的顺序为苯丙氨酸>甘氨酸>丙氨酸e>缬氨酸>正亮氨酸>异亮氨酸。

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