The effect of transition metal ions on the yield of "residual hydrogen" in neutral radiolysis solutions

2-d-2-Propanol has been irradiated in dilute neutral aqueous solutions in the presence of acetone and the yield of HD determined. HD is formed by abstraction of the α-hydrogen of 2-propanol by the "residual hydrogen." In acetone-free acid solutions HD is formed by abstraction of the α-hydrogen of 2-propanol by hydrogen atoms. Ca⁺² and Ba⁺² ions have no effect on the yield of HD in either unbuffered or acidified solutions. On the other hand, in unbuffered solutions, certain transition metal ions diminish the yield of HD in the following order: Ni⁺², Cd⁺², Co⁺², Zn⁺². The same ions were examined in acid solution, where hydrogen atoms are present, and were found to have no effect on the yield of HD. In other words, these metal ions, which were found not to react with hydrogen atoms, do react with the "residual hydrogen" or with its precursor. It is suggested that the "residual hydrogen" or its precursor is actually an excited water molecular, H₂O*, which reacts with these metal ions as a reductant in analogy to their reaction with hydrated electrons.