Knowledge Bank

A second conformer of glycine, the smallest, amino acid, has been observed using millimeter wave spectroscopy. Similar to the first conformer $observed,1,2$ this conformer has an a-type prolate rotor spectrum. The assigned spectral lines from 75-115GHZ have been fit to a centrifugal distortion model with the results: $A\prime \prime =10341.69$(26)MHZ; $B\prime \prime =3876.198$(14)MHZ; and $C\prime \prime =2912.362$(14)MHZ. In addition to the ground state, transitions from a low lying vibrational state $(62\pm 20$ $cm-1$ separation) have been observed up to v=3. The measurement of $\mu =1.1(2)$ Debye allows the calculation of the energy difference of $420\pm 100$ $cm-1$ between the two conformers, with the newly assigned species being the lower in energy. The excellent agreement of the observed molecular parameters with those calculated by Sellers and Sch""afer will be discusse$d.3$