We investigate the molecular geometry of the carboxyl group of formic acid in acetonitrile and aqueous solutions at room temperature with two-dimensional infrared spectroscopy (2D-IR). We found that the carboxyl group adopts two distinct configurations: a configuration in which the carbonyl group is oriented anti-parallel to the hydroxyl (anti-conformer), and a configuration in which the carbonyl group is oriented at an angle of ~60° with respect to the hydroxyl (syn-conformer). These results constitute the first experimental evidence that carboxyl groups exist as two distinct and long-living conformational isomers in aqueous solution at room temperature.

The Netherlands Organisation for Scientific Research (NWO) , European Research Council (ERC)
J. Phys. Chem. Lett.
Ultrafast Spectroscopy

Giubertoni, G., Sofronov, O., & Bakker, H. (2019). Observation of Distinct Carboxylic Acid Conformers in Aqueous Solution. J. Phys. Chem. Lett., 10(12), 3217–3222. doi:10.1021/acs.jpclett.9b00915

Additional Files
16526M_H.Bakker.pdf Author Manuscript , 505kb
16526ESI.pdf Author Manuscript , 634kb