Knowledge Bank

The gas-phase infrared spectrum and the liquid-phase Raman spectrum have been recorded for 1-chlorocyclobutene, which is a newly prepared substance. Much evidence in the literature on cyclobutenes indicates that the cyclobutene ring is essentially planar. The vibrational spectra for 1-chlorocyclobutene are consistent with a planar ring structure and C5 symmetry. The axis of least moment of inertia. la. is essentially parallel to the CCI bond. In the gas-phase infrared spectrum modes of a symmetry have hybrid type-$A\setminus B$ band shapes, and modes of a symmetry have type-C band shapes. As a consequence of structural variety and some symmetry in this molecule, an essentialy complete assignment of vibrational fundamentals is possible. The fundamentals in $cm-1$ are: $(a1)3090,2947,2940,1594,1452,1434,1250$ (average of Fermi resonance doublet). $1192,1164,1120,916,890,869,493,299;(a\alpha \alpha )2980,2966,1070.1016.854,751,(751),395.211$. of particular interest is the ring puckering frequency of $211cm-1$ which compares with $325cm-1$ in cyclobutene itself, $1261cm-1$ in 1- $fluerocyclobutene.2132cm-1$ in 3,3,4,4, $tetrafluorocyclobutene.2$ and $98cm-1$ in $perfiuorocyclobutene3$.