Knowledge Bank

The Raman spectrum of liquid $CF3COCl$ and the infrared spectra of the gas and the condensed solid have been studied, and fundamental frequencies assigned. For assumed $Ca$ symmetry, the a' fundamentals occur at 1811, 1284, 1240, 937, 750, 703, 583, 511, 334, and $198cm-1$, and a'' fundamentals at 1202, 517, 390 and $234cm-1$. The torsional vibration was not observed, although observations were made down to $30cm-1$. Unless the band is so weak as to have escaped detection, this means that the barrier in this molecule is $\le 300cm-1$. Of particular interest is the splitting of the $CF3$ vibrations due to the plane of the molecule. The three C-F stretches were clearly resolved, the most symmetric being the highest in frequency and the stretch antisymmetric to the plane, the lowest. The two asymmetric $CF3$ deformations (degenerate in $C3v$ molecules) are almost $200cm-1$ apart. The spectra of related molecules, such as $(CF3)2C=O,CF3CHO$, and $CF3CONH2$, will also be discussed.