Knowledge Bank

The infrared spectra of polycrystalline $PH4Cl$ and $PD4Cl$ have been recorded from $33cm-1$ to $4000cm-1$ at $-170\circ C$. Raman spectra of the two compounds were also obtained on poly-crystalline samples at the same temperature. Three external modes were observed: an infrared active translation at $140cm-1$, a Raman active translation at $114cm-1$ and a Raman active libration at $370cm-1$. Eight internal modes were also assigned. The barrier to torsional oscillation of the phosphonium ions was calculated from the Raman active libration and was found to be 8.5 kcal/mole for both $PH4$ and $PD4$ ions.