Conformational panorama, experimental structure and molecular properties of the ortho-, meta- and para-isomers of anisaldehyde

The structure of the ortho -, meta - and para -isomers of anisaldehyde, a common benzene derivative, has been investigated by means of their broadband rotational spectra. The conformational landscape of each system was evaluated with the aid of quantum chemical calculations, resulting in a different number of potential conformers for each isomer. The detection of heavy-atom isotopologues has enabled the accurate determination of the experimental gas-phase structure of one conformer of ortho -anisaldehyde, three conformers of meta -anisaldehyde, and two conformers of the para -isomer. The comparison of the molecular structures of the isomers reveals several noteworthy features, including the planar skeleton in all the detected conformers. This feature is directly connected to the antioxidant properties of anisaldehydes, which make them highly valuable in a wide range of applications. The results of this work provide valuable insights into the impact of ortho -, meta -, and para -isomerism on the conformational landscape, molecular structure, aromaticity, and molecular electrostatic potential of a disubstituted aromatic compound.