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Kinetic and mechanistic aspects of the NO oxidation by O 2 in aqueous phase
Author(s) -
Pires Marçlal,
Rossi Michel J.,
Ross David S.
Publication year - 1994
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550261208
Subject(s) - chemistry , reaction rate constant , aqueous solution , autoxidation , kinetics , activation energy , kinetic energy , phenol , nitrosation , aqueous two phase system , organic chemistry , physics , quantum mechanics
The oxidation kinetics of NO by O 2 in aqueous solution was observed using a stopped flow apparatus. The kinetics follows a third order rate law of the form k · [NO] 2 · [O 2 ] in analogy to gas‐phase results. The rate constant at 296 K was measured as (6.4 ± 0.8) · 10 6 M −2 s −1 with an activation energy of 2.3 kcal/mol and a preexponential factor of (4.0 ± 0.5) · 10 8 M −2 s −1 . The rate constant displays a very slight pH dependence corresponding to less than a factor of three over the range 0 to 12. The system NO/O 2 in aqueous solution is an efficient nitrosating agent which has been tested using phenol as a substrate over the pH range 0 to 12. The rate limiting step leading to formation of 4‐nitrosophenol is the formation of the reactive intermediate whose competitive hydrolysis yields HONO or NO 2 − . The absence of NO 3 − in the autoxidation of NO, the exclusive presence of NO 2 − as a product of the nitrosation reaction of phenol, and the kinetic results of the N 3 − trapping experiments point towards N 2 O 3 as the reactive intermediate. © 1994 John Wiley & Sons, Inc.