Microwave spectrum,structure, dipole moment and barrier to internal rotation of methyltrifluorosilane

The rotational spectrum of methyltrifluorosilane in the ground and the first three excited states of the torsional mode have been investigated in the region of 12.5–40.0 GHz. The rotational transitions for the ¹³C isotopic species have also been measured. The following structural parameters have been determined: r(CH) = 1.081 ± 0.004 Å, ∠ HCSi = 111°1' ± 30', r(CSi) = 1.812±0.014 Å, r(SiF) = 1.574 ± 0.007 Å, ∠ FSiC = 112°20'± 1°6'. The structural parameters are compared to the corresponding ones for similar molecules. The dipole moment was determined to be 2.33 ± 0.10 D. From relative intensity measurements, the barrier to internal rotation was found to be 0.93 ± 0.09 kcal mol⁻¹; this value is consistent with the values obtained for other methylfluorosilanes.