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Abstract The mechanisms for the Cl‐initiated and OH‐initiated atmospheric oxidation of t ‐butyl alcohol (TBA), methyl t ‐butyl ether (MTBE), and dimethyl ether (DME) have been determined. For TBA the only products observed are equimolar amounts of H 2 CO and acetone, and its atmospheric oxidation can be represented by (7), equation image The mechanism for the atmospheric oxidation of DME is also straight forward, with the only observable product being methyl formate, equation image The mechanism for the atmospheric oxidation of MTBE is more complex, with observable products being t ‐butyl formate (TBF) and H 2 CO. Evidence is presented also for the formation of 2‐methoxy‐2‐methyl propanal (MMP), which is highly reactive and presumably oxidized to products. The atmospheric oxidation of MTBE can be represented by (9) and (10), equation image equation image In terms of atmospheric reactivity, DME, TBA, and MTBE all compare favorably with methanol. In terms of rate of reaction in the atmosphere, DME, MTBE, and TBA are 1.4, 0.40, and 0.28 times as reactive as CH 3 OH towards OH on a per carbon basis. With regard tochemistry, atmospheric oxidation of CH 3 OH yields highly reactive H 2 CO as the sole carbon‐containing product. In contrast, only 25% of the carbon in TBA is converted to H 2 CO, with the balance yielding unreactive acetone. For DME, all the carbon is converted to methyl formate which is unreactive. Finally, for MTBE, 60% is converted to unreactive TBF while the remaining 40% produces highly reactive MMP. Final assessment of the impact of these materials on the atmospheric reactivity of vehicle emissions requires the determination of their emissions rates under realistic operating conditions.
Japar et al. (Sat,) studied this question.