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Photolysis at 185 nm of dimethyl ether in aqueous solution: involvement of the hydroxymethyl radical

1981; Elsevier BV; Volume: 16; Issue: 4 Linguagem: Inglês

10.1016/0047-2670(81)80051-2

1873-2658

Heinz‐Peter Schuchmann, Clemens von Sonntag,

Atmospheric Ozone and Climate

In the 185 nm photolysis of aqueous solutions of dimethyl ether (saturated at atmospheric pressure; 1.1 M) the following products are formed (quantum yields in parentheses): methane (0.06); hydrogen (0.03); methanol (0.02); 1,2-dimethoxyethane (0.014); formaldehyde (0.012); 2-methoxyethanol (0.012); ethylene glycol (0.009); ethanol (0.005); methyl ethyl ether (0.001). These products are explained by three primary processes (reactions (i) – (iii)), the rearrangement process (reaction (iv)) known to be undergone by alkoxyl radicals in aqueous solution and subsequent free-radical reactions. In aqueous solutions the quantum yield of primary processes leading to products is smaller by about an order of magnitude than those in cyclohexane solutions or those previously found with similar ethers as pure liquids. This apparently means that water as a solvent has a quenching effect. In aqueous solutions there is an excited species which is reactive towards nitrous oxide and a proton, leading to the formation of nitrogen and hydrogen respectively. Free hydrated electrons generated by photoionization do not appear to be involved in these reactions.