Millimetre wave rotational spectrum of glycolic acid

Abstract The pure rotational spectrum of glycolic acid, CH 2 OHCOOH, was studied in the region 115–318 GHz. For the most stable SSC conformer, transitions in all vibrational states up to 400 cm −1 have been measured and their analysis is reported. The data sets for the ground state, v 21 = 1 , and v 21 = 2 have been considerably extended. Immediately higher in vibrational energy are two triads of interacting vibrational states and their rotational transitions have been assigned and successfully fitted with coupled Hamiltonians accounting for Fermi and Coriolis resonances. The derived energy level spacings establish that the vibrational frequency of the ν 21 mode is close to 100 cm −1 . The existence of the less stable AAT conformer in the near 50 °C sample used in our experiment was also confirmed and additional transitions have been measured.