Knowledge Bank

The far infrared spectrum of gaseous trans-1,3-dichloropropene has been recorded at a resolution of $0.10cm-1$ in the region of 350 - 50 $cm-1$. The fundamental asymmetric torsional frequencies of the more stable gauche and the higher energy cis conformations have been observed at 85 and 130 $cm-1$, respectively. Several excited states falling to lower frequencies were observed for the cis conformation. From these data the asymmetric torsional potential function governing the internal rotation about the C-C bond has been determined. From studies of the Raman spectrum at variable temperatures, the conformational enthalpy difference has been determined. A complete assignment of the vibrational fundamentals observed from the infrared spectra (3300 - 50 $cm-1$ of the gas and solid and the Raman spectra (3200 - 10 $cm-1$) of all three physical states is proposed. All of these data are compared to the corresponding quantities obtained from ab initio Hartree-Fock gradient calculations employing both the 3-21$G\ast$ and 6-31$G\ast$ basis sets.