Knowledge Bank

The Raman spectrum of tetrafluorooxirane-$\mathrm{<mrow\; data-mjx-texclass="ORD">16</mrow>}O$ (tetrafluoroethylene oxide-16: TFEO-16) has been obtained at-$80\circ C$. From this spectrum and a previous intrared $study1$ we have developed a complete assignment of the vibrational fundamentals. These fundamentals in $cm-1$ are: $(a1)1610,1161,792,502,320;(a2)1240,516,234;(b1)1128,776,696,528;(b2)1282.558,186$. The newly available Raman spectrum led to revisions in the assignments for $\nu 7,\nu 10.\nu 11$, and $\nu 12$ and the replacement of estimates for $\nu 6$ and $\nu 8-1$ The assignments for $\nu 5,\nu 8$, and $\nu 12$ are supported by values of 306(17). 226(17), and $182(23)cm-1$. respectively, derived from vibrational satelletes in the microwave $spectrum.2$ From the infrared and Raman spectra of TFEO-18 the fundamentals in $cm-1$ are: $(a)1607,1136.789,494,321;(a2)1240,516.234;(b1)1127,777,679.516;(b2)1282,539,185$. Because $\nu 1$ shifts very little with $\mathrm{<mrow\; data-mjx-texclass="ORD">18</mrow>}O$ substitution, this mode is not 'ring breathing-1but is CC stretching presumably raised in frequency by mixing with CF stretching and bond strengthening due to the fluorine substituents. Other modes that depend significantly on $\mathrm{<mrow\; data-mjx-texclass="ORD">18</mrow>}O$ substitution are $\nu 2$ (sym CO stretching), $\nu 11$ and $\nu 12$ (asym CO stretching), and $\nu 14$ (COC Rappping).