A product study of the sonolysis of the volatile substrate t-butanol in aqu
eous solution indicates that substrate decomposition is practically complet
ely determined, even at concentrations as low as millimolar, by oxidative p
yrolysis going on in the gas phase within the collapsing cavitational bubbl
e. OH-Radical-induced reactions in solution are insignificant since the vol
atility of this substrate, its gas-phase concentration within the bubble en
hanced by a certain degree of hydrophobicity, causes OH radicals generated
thermolytically from water vapour to be intercepted before they can reach t
he aqueous phase. The nature of the products, as well as the t-butanol-conc
entration dependence of the product yields, can be qualitatively explained-
on the basis of the t-butanol-pyrolysis mechanism. Kinetic considerations i
nvolving the relative yields of the pyrolysis products ethane, ethylene and
acetylene lead to an estimate of a value of 3600 K for the average pyrolys
is temperature at a t-butanol bulk concentration of 10(-3) molar.