The geometries and vibrational frequencies of two conformers of pyruvi
c acid have been obtained at the ab initio second order Moller-Plesset
level of theory using the 6-311++G* basis set. While the calculated
geometries have been compared to the experimental microwave data, the
vibrational frequencies have been assigned, using the experimental gas
phase IR spectra of 13 isotopes of pyruvic acid by a recently develop
ed scaling procedure (IRPROG). An attempt has been made to explain the
stability of the eclipsed conformation over the staggered conformatio
n of pyruvic acid by taking account of the molecular orbitals. (C) 199
8 Elsevier Science B.V.