posted on 2024-01-17, 20:38authored byWenhao Sun, Pablo Pinacho, Daniel A. Obenchain, Melanie Schnell
We report the spectroscopic investigation of two bifunctional
aliphatic
carboxylic acids, namely, adipic acid and 6-hydroxycaproic acid, in
the gas phase by combining high-resolution rotational spectroscopy
and supersonic expansions. Their pure rotational spectra were successfully
identified and characterized. However, due to the low thermal stability
of these two chemicals, the measured rotational spectra were significantly
congested with transitions corresponding to their decomposition products
upon heating. We observed cyclopentanone and adipic anhydride in the
spectrum of adipic acid and ε-caprolactone
and its monohydrate in the spectrum of 6-hydroxycaproic acid. On the
basis of the distinct fingerprints of both carboxylic acids and a
series of their decomposition products, the spectra were analyzed
in a time-segmented manner. This provides valuable insights into the
thermal decomposition mechanisms of these two samples over time, which
highlights the robustness of microwave spectroscopy as a potent tool
for analyzing complex chemical mixtures in a species-, isomer-, and
conformer-selective way.