Kinetics of hydrogen isotope exchange reactions. Part XIX. Effect of added solutes on aliphatic tritium exchange of t-butyl alcohol(2-methylpropan-2-ol) under the influence of β-radiation, and related experiments

Abstract

The effect of added solutes (AgClO₄, CdSO₄, CuSO₄, NiSO₄, and H₂O₂) on the tritium exchange in the methyl groups of t-butyl alcohol is to decrease the exchange rate very sharply, the silver salt having the most pronounced influence. The inhibitors do not totally suppress the exchange. The results suggest that there are two exchange routes the major one of which is susceptible to inhibition by electron scavengers while the minor one is not. As a working hypothesis it is suggested that the major exchange route involves reaction between the hydrated electron and t-butyl alcohol. This results in the formation of a solvated electron containing one molecule of t-butyl alcohol in the cluster of solvent molecules in which the electron is trapped with consequent hydrogen exchange between the molecules of the cluster. The minor route is envisaged as the direct formation of this mixed solvent cluster by the action of radiation. The scavenger effects suggest that the second-order rate constant for the reaction between t-butyl alcohol and the hydrated electron is ca. 10⁸ l mol^–1 s^–1. Since this reaction does not destroy the solvated electron, the high value deduced is not incompatible with the low rate constants obtained for the destruction of the hydrated electron by alcohols from pulse-radiolysis studies.

Experiments with chemically generated hydroxyl radicals indicate that hydroxyl radicals are not responsible for initiating the radiation-induced exchange.

Most of the results reported refer to partially aerated solutions: degassing increases the amount of exchange obtainable for a given radiation dose.