Infrared Spectra of Gas-Phase 1- and 2‑Propenol Isomers

Fourier transform infrared spectra of isolated 1-propenol and 2-propenol in the gas-phase have been collected in the range of 900–3800 cm–1, and the absolute infrared absorption cross sections reported for the first time. Both cis and trans isomers of 1-propenol were observed with the trans isomer in greater abundance. Syn and anti conformers of both 1- and 2-propenol were also observed, with abundance consistent with thermal population. The FTIR spectrum of the smaller ethenol (vinyl alcohol) was used as a benchmark for our computational results. As a consequence, its spectrum has been partially reassigned resulting in the first report of the anti-ethenol conformer. Electronic structure calculations were used to support our experimental results and assign vibrational modes for the most abundant isomers, syn-trans-1-propenol and syn-2-propenol.