Aquasonolysis of thiophene and its derivatives.

The rate constants and products of the aquasonolysis of thiophene, tetrahydrothiophene, 2-methylthiophene, 2,5-dimethylthiophene, and 2-ethylthiophene have been investigated. The sonolysis of the selected compounds in aqueous solution follows pseudo-first-order kinetics. The aquasonolytical rate constants correlate very well with the water solubility and Henry's Law constants of thiophenes. Surprisingly, vapour pressures and heats of formation of thiophenes have little effect on their aquasonolytical rates. The pseudo-first-order rate constant for the decay of thiophene decreases as its initial concentration increases. These results indicate that the transfer process of organic solutes between cavitation bubbles and the bulk liquid can strongly affect the aquasonolysis. Furthermore, carbon disulfide, diacetylene, and dimers can be detected as common products during ultrasonic irradiations. Hence, the predominant pathway of the aquasonolysis of thiophenes is the pyrolysis during the collapse of cavities.