Knowledge Bank

Tetramethylene cyclobutane, or [4] -radialene, is “figure” Heretofore it has been obtained only in solution. We have succeeded in isolating both it and its perdeutero derivative for the first time. Complete infrared and Raman spectra have been measured. They show convincingly that the molecule has $D\pm$ symmetry---i.e. that it is a planar molecule. This is interesting because (a) some cyclobutane compounds have planar and some have folded rings, and (b) the corresponding perchloro compound is apparently non-planar.