The heavy atom microwave structure of 2-methyltetrahydrofuran

• We measure the molecular beam FT microwave spectra in the ground vibrational state.
• The isotopic substitutions allows determining the microwave structure.
• Cremer-Pople notation was used to describe the ring geometries.
• The experimental results confirm that the ring plane is distorted.

The rotational spectra of 2-methyltetrahydrofuran have been observed using a pulsed molecular beam Fourier transform microwave spectrometer operating in the frequency range 2–26.5 GHz. Conformational analysis using quantum chemical calculations yields two stable conformers; both of them possess an envelope structure. The conformational transformation can occur via two different transition states. The Cremer-Pople notation for five-membered rings is chosen for describing the conformations. Only one conformer with equatorial position of the methyl group is assigned in the experimental spectrum. The fits of its parent species, 13C- and 18O-isotopologues result in highly accurate molecular parameters, and enable the determination of a heavy atom rs structure using Kraitchman’s equations. This experimentally determined structure is in excellent agreement with the structure calculated by anharmonic frequency calculations.

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