Pulsed-beam Fourier transform microwave spectroscopy (PBFTMS) was used to determine the rotational structure of N-hydroxypyridine-2(1H)-thione. PBFTMS was also used to determine the rotational structure of a hydrogen dimer between propiolic acid and formic acid. Rotational constants and quadrupole coupling constants were determined. Calculations (MP2/DFT) were utilized in predicting the isotopic structures. Isotopic data (D, and ¹³C) and normal isotopomers collected were used in establishing of key structural parameters such as bond length and bond angles.