Millimeter wave free-jet spectrum of the isotopologues of 1,2-butanediol

We recorded the rotational spectra of six isotopologues of the most stable conformer of 1,2-butanediol in the 59.6–74.4 GHz frequency region. The observed species are the four monosubstituted 13C, the OD···OH and the OD···OD, and the measurements were performed using a Free-Jet Absorption Millimeter Wave spectrometer. The analysis of the 18 experimental rotational constants determined for all the isotopologues together with those of the parent species, lead to the determination of the coordinates in the principal axis system for the substituted atoms. From the theoretical structure, calculated at the B3LYP-D3/aug-cc-pVTZ level of theory, a refinement of the structural parameters led to a partial r0 geometry, which reproduced all the rotational constants within 1.3 MHz.