VIBRATIONAL SPECTRA OF $CF_{3} Cz \equiv CH, CH_{a} \equiv $CD, AND $CF_{3}\equiv CCF_{3}$

Abstract

“The infrared spectra of gaseous $CF_{3}C \equiv $CH and $CF_{3}C \equiv $CD have been measured from 75 to $4000 cm^{-1}$. The Raman spectrum of liquid $CF_{3}C=CH$ is given with polarizations. The fundamentals frequencies for the latter compound are, for $C_{3v}$ symmetry: $a_{1}: 3330, 2165, 1254, 810$, and $535; e: 1182, 686, 611, 452$, and $171 cm^{-1}$. The infrared spectrum of $CF_{3}C=CCF$ has been extended to $60 cm^{-1}$ to loctae two postulated fundamentals. The entire spectrum has also been examined at grating resolution. Current theory holds that for an ethane-like molecule with free internal rotatin, the effective symmetry of the potential function is $D_{6h}$. Experimental evidence is presented for the actual point group being $D_{3d}$. Therefore either the theory is wrong, or the molecule does not have free internal rotation. The fundamental frequencies for $CF_{3}C \equiv CCF$, are for $D_{3d}$ symmetry: $a_{1_{g}}:2300, 1245, 771, 291; a_{2_{u}}: 1294, 900, 639; e_{g}: 1181, 624, 464, 186; e_{u} :1198,603, 434, 75 cm^{-1}$. The $a_{1}$ torsion was not evaluated; it is presumed to be close to zero. “