Rotational spectrum and intramolecular hydrogen bonding in 1,2-butanedithiol

Abstract The jet-cooled rotational spectrum of 1,2-butanedithiol was observed in the frequency region 2–8 GHz. Two conformers were detected for the molecule, corresponding to anti- and gauche-carbon molecular skeletons, both featuring a gauche arrangement of the two thiol groups. All 13C and 34S monosubstituted isotopologues were additionally assigned in natural abundance for the most stable anti isomer, while only the two 34S species were detected for the weaker gauche conformation. The structural analysis included ground-state effective structures, isotopic substitution coordinates, B3LYP-D3(BJ) density functional molecular orbital calculations and non-covalent interactions mapping with NCIPlot. The structural data confirm that the two thiol groups synchronize their orientation either parallel or antiparallel to support intramolecular S–H⋯S weak hydrogen bonding, reminiscent of the intramolecular hydrogen bond networks observed in adjacent alcohol groups. DFT calculations on 1,2-butanediol and 1,2-ethanedithiol offered structural comparisons with the title compound.