title: Kinetics of the reaction of nitric oxide with oxygen in aqueous solutions.
abstract: 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)
authors.affiliation: Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge 02139.
authors.forename: R S
authors.initials: RS
authors.lastname: Lewis
authors.forename: W M
authors.initials: WM
authors.lastname: Deen
mesh_terms: D007700:Kinetics; D008956:Models, Chemical; D009569:Nitric Oxide / Q000737:chemistry*; D009585:Nitrogen Dioxide / Q000737:chemistry; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D012996:Solutions
chemical_list: D012996:Solutions; D009569:Nitric Oxide; D009585:Nitrogen Dioxide; D010100:Oxygen