The mechanism of oxidation of 3-mercaptopropionic acid
The mechanism of oxidation of 3-mercaptopropionic acid
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DOI：
10.1139/v97-002
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发表时间：
1997-01-01
期刊：
影响因子：
--
通讯作者：
Blesa, MA
中科院分区：
文献类型：
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作者：
Forlano, P;Olabe, JA;Blesa, MA
研究了酸性条件下过氧化氢氧化3-巯基丙酸（3-MPA）的反应机理。硫对过氧键的亲核攻击控制反应速率。外推的pH依赖性表明，由去质子化的二价阴离子的攻击率是最高的。痕量的Fe（III），在低于10（-7）mol dm（-3）的水平下，不能通过单电子机制有效地催化该过程;在更高的浓度下，或在铁（III）氧化物的表面上，这种类型的催化变得重要。采用微分脉冲极谱法和循环伏安法研究了3-MPA的电化学氧化。反应机理为EC_2 E型，第二个电子转移步骤对应于二硫化物RS-SR的氧化。自由基为1.8 × 10（3）mol（-1）dm（3）s（-1）;该步骤的缓慢性与在金属离子的单电子氧化过程中观察到的机理一致。
The mechanism of the oxidation of 3-mercaptopropionic acid (3-MPA) by hydrogen peroxide was studied in the acidic pH range. The nucleophilic attack by sulphur on the peroxide bond controls the rate. Extrapolation of the pH dependency suggests that the rate of attack by the deprotonated dianion is highest. Traces of Fe(III), at levels below 10(-7) mol dm(-3), do not catalyze efficiently the process through one-electron mechanisms; at higher concentrations, or on the surface of iron(III) oxides, this type of catalysis becomes important. The electrochemical oxidation of 3-MPA was also studied, using differential pulse polarography and cyclic voltammetry techniques. The mechanism is of the EC2E type, the second electron transfer step corresponding to the oxidation of the disulphide RS-SR. The rate constant for the dimerization of the RS. radicals was 1.8 x 10(3) mol(-1) dm(3) s(-1); the slowness of this step agrees with the mechanisms observed in the course of one-electron oxidations by metal ions.