A kinetic study of S-nitrosothiol decomposition.
A kinetic study of S-nitrosothiol decomposition.
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DOI：
10.1002/1521-3765(20020118)8:2
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发表时间：
2002-01
期刊：
影响因子：
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通讯作者：
L. Grossi;P. Montevecchi
中科院分区：
文献类型：
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作者：
L. Grossi;P. Montevecchi
在厌氧条件下，S-亚硝基硫醇1a-e通过S-N键的均裂进行热分解;该反应导致以可逆方式形成一氧化氮和硫烷基自由基。速率常数，k（t），已被确定在不同的温度下进行的动力学测量在正烷烃溶剂。叔亚硝基硫醇1c（k1（69 ℃）= 13 x 10（-3）min（-1））和1d（k1（69 ℃）= 91 × 10（-3）min（-1））比伯亚硝基硫醇1a分解更快（k1（69 ℃）= 3.0 × 10（-3）min（-1））和1b（k1（69 ℃）= 6.5 × 10（-3）min（-1））。根据Arrhenius方程计算了反应活化能（E #= 20.5 - 22.8Kcal mol（-1））。在有氧条件下，S-亚硝基硫醇1a-e的衰变通过N2O3催化的自催化链分解过程发生。后者是由双氧与内源性和/或外源性一氧化氮反应形成的。通过去除内源性一氧化氮或通过存在抗氧化剂（如对甲酚、β-苯乙烯和BHT）强烈抑制自催化分解。的速率的链反应是独立的RSNO浓度和减少与增加庞大的烷基，这表明空间效应是至关重要的传播步骤。
Under anaerobic conditions S-nitrosothiols 1a-e undergo thermal decomposition by homolytic cleavage of the S-N bond; the reaction leads to nitric oxide and sulfanyl radicals formed in a reversible manner. The rate constants, k(t), have been determined at different temperatures from kinetic measurements performed in refluxing alkane solvents. The tertiary nitrosothiols 1c (k1(69 degrees C) = 13 x 10(-3) min(-1)) and 1d (k1(69 degrees C) = 91 x 10(-3) min(-1)) decomposed faster than the primary nitrosothiols 1a (k1(69 degrees C) = 3.0 x 10(-3) min(-1)) and 1b (k1(69 degrees C) = 6.5 x 10(-3) min(-1)). The activation energies (E# = 20.5-22.8 Kcal mol(-1)) have been calculated from the Arrhenius equation. Under aerobic conditions the decay of S-nitrosothiols 1a-e takes place by an autocatalytic chain-decomposition process catalyzed by N2O3. The latter is formed by reaction of dioxygen with endogenous and/or exogenous nitric oxide. The autocatalytic decomposition is strongly inhibited by removing the endogenous nitric oxide or by the presence of antioxidants, such as p-cresol, beta-styrene, and BHT. The rate of the chain reaction is independent of the RSNO concentration and decreases with increasing bulkiness of the alkyl group; this shows that steric effects are crucial in the propagation step.