Knowledge Bank

The Raman (3200 to $10cm-1$) spectra of allyl cyanide, $CH2=CHCH2CN$, have been recorded for the gas, liquid and solid phases. Additionally, qualitative depolarization values were measured for the liquid phase. The far infrared spectrum of the gas has been recorded from 350 to $30cm-1$ at a resolution of $0.10cm-1$. The observed bands are assigned on the basis of the more stable cis conformer (cyanide group cis to the double bond) and a less stable gauche conformer in the liquid state. The fundamental asymmetric torsion of the cis conformer has been observed at $141cm-1$ and the potential function governing the conformer interchange is estimated. A complete vibrational assignment is proposed for both conformers based on Raman depolarization data, group frequencies, and normal coordinate calculations. The experimental conformational stability, barriers to internal rotation, fundamental vibrational frequencies. and structural parameters are compared with those obtained from ab initio Hartree-Fock gradient calculations employing the $RHF/3-21G,RHF/6-31G\ast$. and/or $MP2/6-31G\ast$ basis sets and to the corresponding quantities obtained from previous vibrational and structural studies.