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The yields of formaldehyde and methanol from the thermal methanefoxygen reaction at 395°C in a static system were slightly higher with an " activated " than with a " deactivated *' surfam (see part l), though the rate of pressure change was considerably larger. Appreciable amounts of methylhydroperoxide were present in the products with the " activated " surface only. The decomposition of this hydroperoxide at 395°C gave formaldehyde, methanol, water and probab:y oxygen. The half-life was about 30 sec with an activated surface (the IHCHO]/[CH3OH] ratio in the products being about unity) and 5-10 sec with a deactivated surface ([HCHO]/[CH3OH] about 4). Some 14CHq was formed during the photo-initiated oxidation using (14CH3)2CO. This fact and the variation of the yield with conditions shows that hydrogen abstraction by methyl radicals was competing with their relatively slow oxidation.The reactions of methyl and methylproxy radicals, the processes giving formaldehyde, methanol, methylhydroperoxide and the role of the hydroperoxide in the uncatalyzed and photo-irjtiated oxidation of methane are discussed. In the initial stages CH3O2 radicals probably decompose to give HCHO, but later also abstract hydrogen from the aldehyde to give CH300H, which is rapidly removed at a " deactivated " surface, but may decompose homogeneously, ifthe surface is " activated ", to give CH3O radicals which oxidize or abstract hydrogen mainly from formaldehyde to give methanol.

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The reaction of methane and oxygen at about 400°C catalyzed by the photodecomposition of acetone has been studied using a static system. With a new vessel at 414°C the thermal reaction was negligible and the maximum rate of pressure change Lax) was proportional to and independent of the intensity of the ultra-violet radiation. The products were carbon monoxide, carbon dioxide, water, formaldehyde and methanol, the concentration of the last two rising to a maximum and the alcohol not being formed until after the initial stages of the reaction. After many expsriments the thermal reaction became relatively rapid and the temperature was reduced to 395°C. Both the rate and the products of oxidation now depended on the pretreatment of the surface. After a number of photo-initiated oxidations (" activated " surface) appreciable amounts of hydrogen peroxide and methylhydroperoxide were present in the products and the yield of methanol was considerable. After a number of thermal C h -0 2 reactions (" deactivated " surface) the rate of a subsequent photo-initiated reaction and the alcohol yield was much less and no peroxides were detected in the products. With an " activated " surface the kinetics were different ; in particular, pmax rose to a flat maximum on increasing the methane concentration.The oxidation is almost certainly a chain process with degenerate branching. Possible elementary reactions occurring in the system and the effect of surface are discussed. Most of the C02 probably comes from the reaction of CH3COCH2 radicals and oxygen. It is likely that with a " deactivated "

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