H/D isotope exchange in the D2-H2O system under the influence of ultrasound

Water was irradiated by 300-kHz ultrasound under atmospheres of argon, deuterium, and mixtures of the two gases, and the isotopic composition of the gas was determined. The yields of H2 and HD increase with increasing deuterium content of the gas mixture, reach maxima at 35% D2 (H2) and 60% D2 (HD), and fall off at higher D2 concentrations. The yield of the D2 consumption peaks at 50% D2. The absolute yields are greater by almost one order of magnitude than those of ordinary sonolytic reactions such as H2O2 formation. The results are explained by reactions of the H and OH radicals generated in the sonolysis of water. In the absence of deuterium, a large percentage of these radicals recombine. D2 at low concentrations scavenges mainly OH radicals, the principal products being H2 and HDO. At higher D2 concentrations, D2 also scavenges H atoms, the principal products now being HD and HDO. The decrease in all yields at higher D2 concentrations is explained by the lower temperatures reached in the gas bubbles, which are formed by cavitation. 9 references, 1 figure