Extending the Millimeter/Submillimeter Wave Spectrum of Ground State Pyruvic Acid for Comparison to Astronomical Data

The ground state millimeter/submillimeter rotational spectrum of pyruvic acid, a potential interstellar precursor to alanine, was collected and assigned from 90 GHz to 1 THz with extension of the assignments up to maximum J = 99, Ka = 49, and Kc = 99. Previous work on pyruvic acid collected and assigned its spectrum up to 314 GHz with maximum J = 70, Ka = 42, and Kc = 70. Fitting was conducted using the ERHAM program due to the presence of an internally rotating methyl group. This fit resulted in the refinement of the rotational constants making the spectrum of pyruvic acid well-predicted across the entire spectral range of ground-based far-IR telescopes. A subsequent search for pyruvic acid in 30 different astronomical sources was conducted using the results from the experimental spectrum. No definitive detection of pyruvic acid was identified. The results of the laboratory and observational work are presented herein and discussed in the context of prebiotic astrochemistry.