KINETICS OF NITRIC-OXIDE AUTOXIDATION IN AQUEOUS-SOLUTION IN THE ABSENCE AND PRESENCE OF VARIOUS REDUCTANTS - THE NATURE OF THE OXIDIZING INTERMEDIATES
KINETICS OF NITRIC-OXIDE AUTOXIDATION IN AQUEOUS-SOLUTION IN THE ABSENCE AND PRESENCE OF VARIOUS REDUCTANTS - THE NATURE OF THE OXIDIZING INTERMEDIATES
复制标题
DOI：
10.1021/ja00154a007
复制
发表时间：
1995-12-13
影响因子：
15
通讯作者：
CZAPSKI, G
中科院分区：
文献类型：
--
作者：
GOLDSTEIN, S;CZAPSKI, G
的反应。已通过停流法研究了水溶液中存在和不存在各种还原剂的情况下与 O-2 的 NO。亚硝酸盐自氧化过程中测得的产率。 NO 与反应1:4 一致。 NO + O-2 + 2H(2)O --> 4NO(2)(-) + 4H(+)。动力学研究表明，速率定律为-d[O-2]/ dt=k(l)[。 NO](2)[O-2]，k(l)=2.9 x 10(6) M(-2) S-1，22℃，不受 pH 值和亚铁氰化物或 ABTS 存在的影响，亚铁氰化物或 ABTS 在该系统中分别被氧化为铁氰化物和 ABTS(+)。在极限浓度下。不，速率定律是-d[。否]/dt = 4k(l)[。 NO](2)[O-2]，还原为2k(l)[。 NO](2)[O-2] 在亚铁氰化物或 ABTS 存在下。亚铁氰化物存在下的竞争动力学研究结果表明，氧化中间体是 。 NO2，而在 ABTS 存在的情况下，既是 ONOONO，又是 的前体。二氧化氮，和。 NO2 是氧化实体。 pH 值和磷酸盐缓冲液浓度对氧化产率和速率的影响表明，这些系统中形成了 N2O3，因为 OH- 和 HPO42- 都会提高 N2O3 的水解速率。所有数据均与ONOONO的形成一致。 NO2 和 N2O3 作为 的自氧化过程中的氧化中间体。不。这些中间体在氧化过程中的作用取决于这些中间体与底物的反应的相对速率以及自氧化过程的不同步骤的相对速率。详细的自氧化机制。给出并讨论“否”。
The reaction of . NO with O-2 has been investigated in the absence and presence of various reductants in aqueous solution by the stopped-flow method. The measured yield of nitrite during the autoxidation of . NO is in agreement with reaction 1: 4 . NO + O-2 + 2H(2)O --> 4NO(2)(-) + 4H(+). Kinetic studies show that the rate law is -d[O-2]/ dt=k(l)[. NO](2)[O-2] with k(l)=2.9 x 10(6) M(-2) S-1 at 22 degrees C, which was unaffected by pH and by the presence of either ferrocyanide or ABTS, which are oxidized in this system to ferricyanide and ABTS(+), respectively. Under limiting concentrations of . NO, the rate law is -d[. NO]/dt = 4k(l)[. NO](2)[O-2], and it is reduced to 2k(l)[. NO](2)[O-2] in the presence of ferrocyanide or ABTS. The results of the competitive kinetic studies in the presence of ferrocyanide demonstrate that the oxidizing intermediate is . NO2, whereas in the presence of ABTS both ONOONO, which is the precursor of . NO2, and . NO2 are the oxidizing entities. The effect of pH and phosphate buffer concentrations on the oxidation yields and rates suggests the formation of N2O3 in these systems, as both OH- and HPO42- enhance the rate of hydrolysis of N2O3. All data were consistent with the formation of ONOONO,. NO2, and N2O3 as oxidizing intermediates during the autoxidation of . NO. The role of each of these intermediates in the oxidation process depends on the relative rates of the reactions of these intermediates with the substrate and those of the different steps of the autoxidation process. A detailed mechanism for the autoxidation of . NO is given and discussed.