Scavenger studies on the radiolytic hydrogen radical and its precursor in aqueous solution using riboflavin

The measurement of the reaction rate constants of hydrogen radical in neutral solutions has been a difficult task, frequently involving the measurement of H2 and the subtraction of the molecular hydrogen yield. Riboflavin was used as a standard solute in the competition kinetic method to measure GH. This study found that the reaction rate constant for hydrogen radical and alanine was 1.2 x 106 dm3mol-1s-1, while the reaction rate for acetone and the hydrogen radical was 1.0 x 106 dm3mol-1s-1. The Schwarz model on the radiolysis of water proposes that hydrogen radical is produced from a reaction of the solvated electron and the hydronium ion. The effect of various electron scavengers was used to measure the effect on the hydrogen radial yield. The results of this study contradict the solvated electron as a precursor to the hydrogen atom in neutral solutions. Cadmium, acetone and zinc, solutes which do not react with the hydrogen radical but react rapidly with the solvated electron, depleted the hydrogen radical yield with equal efficiency although their solvated electron reaction rate constants are 5.8 x 1010, 5.9 x 109 and 1.0 x 109 dm3mol-1s-1 respectively