Tschuikow-Roux, E.; Rauk, A. J. Phys. Chem. 1991, 95,9832. (b) Chen, Y.; Rauk, A.; Tschuikow-Roux, E. J. Phys. Chem. 1991, 95.9900. (1 5) Pople, J. A.; Head-Gordon, M.; Fox, D. J.; Raghavachari, K.; Curtis, (16) Corbett, P.; Tarr, A. M.; Whittle, E.A manganese-catalyzed Belousov-Zhabotinskii (BZ) reaction with a mixed hypophosphite/acetone substrate was found to be remarkably sensitive to stirring in a batch reactor. The reaction d a t e d in a container with a gas/liquid interface (either air or nitrogen). However, when the reaction was stirred in a sealed flask with no interface, the system remained in the reduced state. When the slow stirring (about 100 rpm) was stopped, a pink color from Mn(II1) was observed to ascend from the Teflon-coated stir bar. When a glass stir bar was used, the system would oxidize much more slowly than with the Teflon one. A possible mechanism is considered in which bromine loss to the gas phase is crucial for oscillation. In the sealed system, oxidation occurs when the stirring is stopped because bromine can adsorb to the surface of the Teflon, allowing local oxidation which spreads throughout the system.