The microwave spectrum of the low energy conformers of 1-ethylsilacyclopentane

The microwave rotational spectrum of 1-ethylsilacyclopentane has been observed using chirped-pulse, Fourier transform microwave spectroscopy and has been reported for the first time. The lowest three energetic conformers were observed and fit to a Watson S semirigid Hamiltonian to within experimental accuracy. The quantum chemical calculations are all within ≈1% of the determined rotational constants, providing confidence that they are accurate representations of the experimental structure. Centrifugal distortion terms D_JK and D_K, although seemingly large, have been determined to be physically meaningful as no apparent evidence such as splittings in the spectrum or transition broadening was observed. A second moment analysis was undertaken and compared to similar silacyclopentanes, but it is not clear if this species follows previously determined trends.