激进的
催化作用
化学
化学计量学
反应速率常数
二甲基亚砜
无机化学
砜
反应机理
动力学
羟基自由基
光化学
药物化学
有机化学
量子力学
物理
作者
Hajem Bataineh,Oleg Pestovsky,Andreja Bakač
出处
期刊:Chemical Science
[The Royal Society of Chemistry]
日期:2012-01-01
卷期号:3 (5): 1594-1594
被引量:328
摘要
A major pathway in the reaction between Fe(II) and H2O2 at pH 6–7 in non-coordinating buffers exhibits inverse kinetic dependence on [H+] and leads to oxidation of dimethyl sulfoxide (DMSO) to dimethyl sulfone (DMSO2). This step regenerates Fe(II) and makes the oxidation of DMSO catalytic, a finding that strongly supports Fe(IV) as a Fenton intermediate at near-neutral pH. This Fe(IV) is a less efficient oxidant for DMSO at pH 6–7 than is (H2O)5FeO2+, generated by ozone oxidation of Fe(H2O)62+, in acidic solutions. Large concentrations of DMSO are needed to achieve significant turnover numbers at pH ≥ 6 owing to the rapid competing reaction between Fe(II) and Fe(IV) that leads to irreversible loss of the catalyst. At pH 6 and ≤0.02 mM Fe(II), the ratio of apparent rate constants for the reactions of Fe(IV) with DMSO and with Fe(II) is ∼104. The results at pH 6–7 stand in stark contrast with those reported previously in acidic solutions where the Fenton reaction generates hydroxyl radicals. Under those conditions, DMSO is oxidized stoichiometrically to methylsulfinic acid and ethane. This path still plays a role (1–10%) at pH 6–7.
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