Thermal unimolecular decomposition of β-butyrolactone (4-methyloxetan-2-one)

Abstract

The thermal decomposition of β-butyrolactone has been studied in the temperature range 209–250 °C. At each temperature, runs were carried out from 10 Torr to < 0.1 Torr. In an aged reaction vessel the decomposition was homogeneous and yielded propene and carbon dioxide as the only products. All the experimental evidence indicated that the reaction was a true unimolecular decomposition which at 10 Torr was close to its high-pressure limit.

The Arrhenius equation corresponding to this limit is log (k_∞/s^–1)= 14.39 ± 0.10–(163.4 ± 1.0) kJ mol^–1/RT ln 10. Arrhenius parameters are also reported for the reaction some way into the fall-off region. The experimental fall-off curves are compared with those calculated from RRKM theory and some discussion about the deviations between theory and experiment is presented. The mechanism of the reaction is considered and the results obtained in this work compared with those reported for β-propiolactone.