Mechanism of the formation of acetaldehyde and butanediol in the radiolysis of ethanol

Abstract

The yields of the major products of the radiolysis of pure ethanol at low doses (4 × 10¹⁷eV/ml.) are: G(H₂) 5·0, G(MeCHO) 3·2, and G(MeCHOH)₂ 1·7. The glycol yield is independent of dose up to 10²⁰eV/ml. but G values of the other products decrease with increasing dose by about one unit each to well defined plateaux. Above 10²⁰eV/ml. all values show a further decrease. The variation in previously reported yields is partially explained by this dose effect. Studies of the effects of ferric chloride, oxygen, and carbon dioxide indicate that dimerisation of hydroxyethyl radicals is the only source of this product and that disproportionation of these radicals accounts for about half the acetaldehyde yield. The rate constants for dimerisation and disproportionation are approximately equal. The unscavengeable yields of hydrogen and acetaldehyde are equivalent, and studies of the effect of carbon monoxide suggest that these are obtained by two different processes. The data from this system also indicate that the ethanol parent ion reacts with the substrate both by proton transfer and by hydrogen abstraction.