A rotational study of the 1:1 adduct of ethanol and 1,4-dioxane

The pure rotational spectra of the 1:1 ethanol – 1,4-dioxane complex and its OD mono-deuterated species have been measured using pulsed-jet Fourier transform microwave spectroscopy. Conformational predictions for the plausible isomers of ethanol – 1,4-dioxane have been carried out considering the spatial orientation of gauche/trans ethanol with respect to the chair/boat and twisted conformations of 1,4-dioxane. Using Helium for the supersonic expansion, the microwave spectrum has been observed for the most stable structure. In the observed isomer, the two subunits are linked together by an O–H⋯O hydrogen bond with gauche ethanol acting as proton donor to dioxane in the chair conformation. The non-covalent interactions have been characterized using different computational approaches. A small inverse Ubbelohde effect was observed after H → D isotopic substitution in the O–H⋯O hydrogen bond.