The Wall Effect on Hydrogen Formation in the Vapour‐Phase Radiolysis of c‐C₆D₁₂ and n‐C₇D₁₆

Vapour‐phase radiolysis of c ‐C 6 D 12 and n ‐C 7 D 16 leads to a relatively large HD yield, up to ∼ 20% of the total hydrogen, which cannot be accounted for by incomplete deuteration of c ‐C 6 D 12 and n ‐C 7 D 16 . In order to elucidate the mechanism of the HD formation, we have examined the effect of additives and of physical conditions on the HD yield. By coating the vessel with a layer of Aquadag the HD yield is greatly decreased without appreciable variation of the total hydrogen yield. The HD yield from nontreated vessels also decreases remarkably with increasing total dose; it is increased upon the addition of traces of water; and is less affected by small amounts of c ‐C 6 H 12 . The addition of SF 6 selectively reduces the HD yield. These experimental results lead us to conclude that inert hydrocarbon ions react by proton transfer with water desorbed from the vessel wall to give hydronium ions which yield HD on subsequent neutralization.