The Mechanism of Methyl Hydroperoxide Formation in the Photoöxidation of Azomethane at 25°

The Thermal Decomposition of Methyl Hydroperoxide

“…If the main reactions in the system are [I], [2], [3], [4], and [12], and if [I] and [12] are assumed t o be first order, then the first order rate constants for reaction [I] may be calculated as described in the previous section. These rate constants are s h o~n in Table I together with the total first order constants.…”

“…Although the mechanism of its production has not been unan~biguously established, and indeed inay not be unique, methyl hydroperoxide has now been recognized as a significant product in the low temperature ( I ) , radiolytic (2), and mercury photosensitized oxidation (3) of methane, the photooxidation of azomethane (4,5), acetone (6), and methyl iodide (7), and the oxidation of methyl radicals (8). Although frequently not found in the products, it seeins likely to be formed in any system involving methyl radicals and oxygen below about 400 "C. The possibility that methyl hydroperoxide acts as a chainbranching agent in the low temperature oxidation of methane has been in dispute and appears to be still uncertain (9).…”

A quantitative study of alkyl radical reactions by kinetic spectroscopy. II. Combination of the methyl radical with the oxygen molecule

“…The product methyl hydroperoxide has been reported in a number of continuous photolysis systems, although there is uncertainty as to its method of formation. Subbaratnam and Calvert [32] suggest that it is formed in the reaction where RH is the parent of the original methyl radical. Sleppy and Calvert [7] did not detect methyl hydroperoxide as a product in their flash photolysis system.…”

“…It is probable that the abstraction reaction (1 1) will have a considerable activation energy if R H is the methyl radical source, but a much smaller activation energy if R H is formaldehyde [28], a product of the reaction. As the continuous photolysis studies at 25°C were for relatively long periods of time [32,33], the abstraction reaction with formaldehyde would be favored. Barnard and Cohen [l 11 conducted their experiments at 200°C and above, where abstraction from the methyl radical source would be more favorable.…”

Photo-oxidation of Iodomethane in Solid Argon

“…We expect the 0-0 bond to be much more susceptible to rupture by near ultraviolet radiation, copiously emitted by the HPK 125 lamp, than the I=O bond. H312COOH and D 3 ' 2 C O~D absorb a t 820 and 794 cm-I respectively (20); the measured deuterium shifts are much smaller. Other peroxides expected to absorb in this region are the radical H3CO0 and its iodide H,COOI.…”