Kinetics of the reactions of propionylperoxy radicals with NO and NO sub(2): peroxypropionyl nitrate formation under laboratory conditions related to the troposphere

• Published in: Environmental science & technology Vol. 31; no. 10; pp. 2949 - 2953
• Main Authors: Seefeld, S, Kerr, JA
• Format: Journal Article
• Language: English
• Published: 01.10.1997
• ISSN: 0013-936X

Peroxyacyl nitrates [RC(O)OONO sub(2)] are formed in the atmosphere in the oxidative degradation of many organic compounds of both anthropogenic and biogenic origin. They are important oxidant components of photochemical smog and can cause eye irritation and plant damage. Moreover, peroxyacyl nitrates act as temporary reservoirs for reactive intermediates involved in photochemical smog formation, and they play an important role in the transport of NO sub(x) in the troposphere. It is therefore essential to establish reliable data on the kinetics and mechanisms of their formation and removal for inclusion in models of atmospheric chemistry. The kinetic data base for the most atmospherically abundant of the series, acetylperoxy nitrate [CH sub(3)C(O)OONO sub(2), PAN], is quite well established, but data are lacking for the higher homologues, e.g., peroxypropionyl nitrate [CH sub(3)CH sub(2)C(O)O sub(2)NO sub(2), PPN], which has also been detected in the troposphere. Here we report data on a relative rate study of the reactions CH sub(3)CH sub(2)C(O)O sub(2) times + NO sub(2) + M arrow right CH sub(3)CH sub(2)C(O)O sub(2)NO sub(2) +M (1) and CH sub(3)CH sub(2)C(O)O sub(2)* + NO arrow right CH sub(3)CH sub(2)* + CO sub(2) + NO sub(2) (2) carried out in an atmospheric flow system in which the relative yields of CH sub(3)CH sub(2)C(O)O sub(2)-NO sub(2) (PPN) have been measured as a function of the ratio of reactants [NO]/[NO sub(2)]. Over the temperature range 249-302 K, at a total pressure of approximately 1 atm, the ratio was independent of temperature with a mean value of k sub(1)/k sub(2) = 0.43 plus or minus 0.07, where the error limits are 2 sigma . This ratio is 1.05 times higher than the corresponding ratio for PAN. In a second type of experiment involving the relative rates of formation of PPN and PAN in the flow system, as a function of [NO]/[NO sub(2)], the value (k sub(1)/k sub(2)) sub(PPN)/(k sub(1)/k sub(2)) sub(PAN) = 0.89 plus or minus 0.13 was determined. The results are discussed with reference to literature data of k sub(1)/k sub(2) for PPN and PAN.