Inversion of Bicyclic Decanes: Rotational Spectra of the Trans and Double Cis Conformations of 2‐Decalone

The conformational landscape of the bicyclic molecule 2‐decalone has been studied in a jet‐cooled expansion by using rotational spectroscopy. The investigation covered the frequency region 7–19 GHz using broadband fast‐passage IMPACT Fourier‐transform microwave techniques. The introduction of the asymmetric carbonyl substituent in the double‐chair decalin skeleton originates two distinct inverting conformers with cis ring junction, which were independently identified and characterized in the gas phase. Additionally, a single trans conformer was detected, as expected for the non‐inverting equatorial ring junction. Accurate rotational parameters and quartic centrifugal distortion constants have been determined for the three observed species. A population estimation is given for the observed conformations based on relative intensities. Supporting ab initio calculations up to MP2/cc‐pVTZ complement the experimental work. Competing for conformational space: Rotational spectroscopy supplemented by ab inito calculations were employed to study the conformational landscape of the bicyclic molecule 2‐decalone. Two inverting double‐chair cis isomers were found to compete with the rigid trans conformation in the conformational space of 2‐decalone.