Reaction of methoxy radicals with oxygen. I. Using dimethyl peroxide as a thermal source of methoxy radicals

✍ Scribed by L. Batt; G. N. Robinson

• Book ID: 102446956
• Publisher: John Wiley and Sons
• Year: 1979
• Tongue: English
• Weight: 372 KB
• Volume: 11
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550111003

✦ Synopsis

Abstract

Using dimethyl peroxide as a thermal source of methoxy radicals overthe temperature range of 110–160°C, and the combination of methoxy radicals and nitrogen dioxide as a reference reaction:
equation image
a value was determined of the rate constant for the reaction of methoxy radicals with oxygen:
equation image
is independent of nitrogen dioxide or oxygen concentration and added inert gas (carbon tetrafluoride). No heterogeneous effects were detected. The value of k~4~ is given by the expression
In terms of atmospheric chemistry, this corresponds to a value of 10^5.6^ M^−1^·sec^−1^ at 298 K. Extrapolation to temperatures where the combustion of organic compounds has been studied (813 K) produces a value of 10^7.7^ M^−1^·sec^−1^ for k~4~. Under these conditions, reaction (4) competes with hydrogen abstraction or disproportionation reactions of the methoxy radical and its decomposition (3):
equation image
In particular k~3~ is in the falloff region under these conditions. It is concluded that reaction (4) takes place as the result of a bimolecular collision process rather than via the formation of a cyclic complex.