Use of a stopped-flow technique to measure the rate constants at room temperature for reactions between the nitrate radical and various organic species
Use of a stopped-flow technique to measure the rate constants at room temperature for reactions between the nitrate radical and various organic species
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使用停流技术测量室温下硝酸根与各种有机物质之间反应的速率常数
DOI：
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发表时间：
1991
期刊：
影响因子：
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通讯作者：
M. Wilson
中科院分区：
文献类型：
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作者：
A. A. Boyd;C. E. Canosa;A. D. King;R. Wayne;M. Wilson
采用停流装置，在λ= 662 nm处用光吸收法检测NO_3，测定了室温下NO_3在乙烯、简单烷烃和氯代甲烷体系中的反应总速率常数。与乙烯反应的模型导致第一步的速率常数为（1.7 ± 0.5）× 10-16 cm 3 molecule-1 s-1。然而，对于由NO3从饱和有机物质中提取H原子，在5-20 s的反应时间内发生的广泛且很大程度上未量化的次级化学反应意味着只能准确评估初级速率常数的上限（假定化学计量因子为2或更多）。在室温下得到的乙烷、丙烷、异丁烷（2-甲基丙烷）、丙酮、二氯甲烷和氯仿的值分别为（以10-17 cm 3分子-1 s-1为单位）2.7 ± 0.2、4.8 ± 1.7、60 ± 10、0.85 ± 0.25、0.48 ± 0.10和6.0 ± 0.5。对于NO3与乙烷和丙烷的反应，动力学模型的主要速率常数的下限估计为（1.1 ± 0.2）和（2.2 ± 0.2）× 10-17 cm-3 molecule-1 s-1。没有观察到NO3和甲烷或氯甲烷之间的反应，这表明这些反应的总速率常数的上限（基于噪声水平）为8 × 10-19和1 × 10-18 cm 3 molecule-1 s-1。
A stopped-flow apparatus, in which NO3 was detected by optical absorption at λ= 662 nm, has been used to measure overall rate constants at room temperature for reaction of NO3 in systems involving ethene, simple alkanes and chlorinated methanes. Modelling of the reaction with ethene led to a rate constant for the primary step of (1.7 ± 0.5)× 10–16 cm3 molecule–1 s–1. However, for H-atom abstraction by NO3 from the saturated organic species, the extensive and largely unquantified secondary chemistry occurring over reaction times of 5–20 s meant that only upper limits for the primary rate constants could be accurately assessed (the stoicheiometric factor being assumed to be two or more). The values thus obtained at room temperature were (in units of 10–17 cm3 molecule–1 s–1) 2.7 ± 0.2, 4.8 ± 1.7, 60 ± 10, 0.85 ± 0.25, 0.48 ± 0.10 and 6.0 ± 0.5 for ethane, propane, isobutane (2-methylpropane), acetone, dichloromethane and chloroform. For the reaction of NO3 with ethane and propane, modelling of the kinetics led to estimates of lower limits of the primary rate constants of (1.1 ± 0.2) and (2.2 ± 0.2)× 10–17 cm3 molecule–1 s–1. No reaction was observed between NO3 and methane or chloromethane, suggesting upper limits (based on the noise levels) for the overall rate constants of these reactions of 8 × 10–19 and 1 × 10–18 cm3 molecule–1 s–1.