Theoretical study of the pressure dependent rate constants of the thermal decomposition of β-propiolactone

A theoretical study of the thermal decomposition of β-propiolactone is carried out using ab initio molecular orbital (MO) methods at the MP2/6-311+G∗∗ level and Rice–Ramsperger–Kassel–Marcus (RRKM) theory. The reported experimental results showed that decomposition of β-propiolactone occurred by three competing homogeneous and first order reactions. For the three reactions, the calculation was also performed at the MP2/6-311+G∗∗ level of theory, as well as by single-point calculations at the B3LYP/6-311+G∗∗//MP2/6-311+G∗∗, and MP4/6-311+G∗∗//MP2/6-311+G∗∗ levels of theory. The fall-off pressures for the decomposition in these reactions are found to be 2.415, 9.423 × 10−2 and 3.676 × 10−3 mmHg, respectively.