A Scent of Peppermint—A Microwave Spectroscopy Analysis on the Composition of Peppermint Oil Krin, Anna Quesada Moreno, María del Mar Peppermint oil Microwave spectroscopy Substitution structure Microwave three-wave mixing Structural analysis Essential oils have a vast number of applications in different areas of our daily life. Detailed chiral analysis and structural characterization of their constituents remains an important subject in analytical chemistry. Here, we report on a broadband rotational spectroscopy study of peppermint oil in the frequency range 2–8 GHz. We focus on an unambiguous determination of the excess enantiomers of the oil constituents menthone and isomenthone in the oil by applying chiralitysensitive rotational spectroscopy, the so-called microwave three-wave mixing (M3WM) technique. Additionally, a new menthol conformer, not previously characterized, was experimentally observed, and the gas-phase structures of the two conformers of menthol and menthone were determined experimentally based on the assignment of their 13C-isotopologues in natural abundance. 2022-07-27T11:30:42Z 2022-07-27T11:30:42Z 2022-06-18 journal article Krin, A... [et al.]. A Scent of Peppermint—A Microwave Spectroscopy Analysis on the Composition of Peppermint Oil. Symmetry 2022, 14, 1262. [https://doi.org/10.3390/sym14061262] http://hdl.handle.net/10481/76387 10.3390/sym14061262 eng http://creativecommons.org/licenses/by/4.0/ open access Atribución 4.0 Internacional MDPI