Lewis R S, Deen W M
Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge 02139.
Chem Res Toxicol. 1994 Jul-Aug;7(4):568-74. doi: 10.1021/tx00040a013.
An understanding of the rate of reaction of nitric oxide (NO) with oxygen in aqueous solutions is needed in assessing the various actions of NO in the body. A novel approach was developed for studying the kinetics of this reaction, which permitted simultaneous and continuous measurements of the concentrations of NO and the principal product, nitrite (NO2-). Nitric oxide was measured using a chemiluminescence detector, with continuous sampling achieved by diffusion of NO through a membrane fitted into the base of a small, stirred reactor. The results with various initial NO and O2 concentrations confirmed that the rate of reaction is second-order in NO and first-order in O2. The rate of reaction of NO was described by the expression 4k1 [NO]2[O2], where k1 was (2.1 +/- 0.4) x 10(6) M-2 s-1 at 23 degrees C and (2.4 +/- 0.3) x 10(6) M-2 s-1 at 37 degrees C. The value of k1 was the same at pH 4.9 and 7.4. The rate of formation of NO2- equaled the rate of reaction of NO (within experimental uncertainty of a few percent), and there was no detectable formation of nitrate (NO3-). This confirmed that NO and NO2- were the only NOx species present in significant amounts and supported the validity of pseudo-steady-state assumptions for NO2 and N2O3, which are intermediates in the conversion of NO to NO2-.(ABSTRACT TRUNCATED AT 250 WORDS)
为评估一氧化氮（NO）在体内的各种作用，需要了解其在水溶液中与氧气的反应速率。开发了一种新方法来研究该反应的动力学，该方法能够同时连续测量NO和主要产物亚硝酸盐（NO2-）的浓度。使用化学发光检测器测量NO，通过将NO扩散通过安装在小型搅拌反应器底部的膜来实现连续采样。不同初始NO和O2浓度的结果证实，反应速率对NO为二级，对O2为一级。NO的反应速率由表达式4k1 [NO]2[O2]描述，其中k1在23℃时为(2.1±0.4)×10(6) M-2 s-1，在37℃时为(2.4±0.3)×10(6) M-2 s-1。k1在pH 4.9和7.4时的值相同。NO2-的形成速率等于NO的反应速率（在百分之几的实验不确定度范围内），且未检测到硝酸盐（NO3-）的形成。这证实了NO和NO2-是大量存在的仅有的氮氧化物物种，并支持了对NO2和N2O3（NO转化为NO2-过程中的中间体）的准稳态假设的有效性。（摘要截短至250字）
