Under the influence of tritium (3-radiation, 1,4-dioxan undergoes hydrogen exchange with the solvent water. The inhibition of the reaction by known electron scavengers (Ag+, Cu2+, Ni2+, Co2+, Zn2+, H.^0 and also by species with high reactivity towards hydroxyl radicals but negligible reactivity towards solvated electrons (N^~, Br~, SON-) has been examined in detail. y-Irradiation similarly induces hydrogen exchange. The action of scavengers is interpreted as requiring the involvement of two

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... rately scavengeable prim ary radiolysis products in the sequence of reactions leading to exchange. Evidence is presented th a t the reactions of these species occur in spur regions, and the scheme 6aq HTO R H + OH*----->R ' + H 20 -----»R~-----»RT is considered to explain the main features of the mechanism. The presence of electron scavengers, even a t high concentration, does not totally inhibit the exchange, and a secondary exchange route, involving a lower valency state of inhibitor cations, is considered responsible for the ' unscavengeable ' portion of the reaction, by providing an alternative exchange route, e.g. HTO R ' + m +----> R~ + Ni2+-----> RT Analogies are drawn between the exchange reaction and other radiationinduced reactions th a t are thought to involve spur processes (such as the formation of H 20 2 as a molecular product in the radiolysis of water). Some implications of the present results for the interpretation of radiationchemical studies in water-alcohol mixtures are indicated.