Knowledge Bank

Rotational transitions with large splittings attributed to internal rotation of the Methyl group have been assigned in the microwave spectra of $CH3OPF2$, $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}CH3OPF2$, and $CD3OPF2$. The effective rotational constants for the A levels of the parent species are A = 5988.97 MHz, B = 3641.80 MHz, and C = 3127.90 MHz. The barrier to internal rotation of the methyl group is $V3=433\pm 20$ cal/mole. The structure of the molecule and the analysis of the internal rotation splittings will be discussed.