Conformational Studies of Cyclobutane Systems

Isolated attempts have been made to detect the presence of nonplanarity in cyclobutane rings. Significant deviations from planarity have been measured for cyclobutane, octafluorocyclobutane, octachlorocyclobutane and bromocyclobutane. The results in the first two cases, however, have not been without controversy. It was the object of the present work to devise a fairly general, but still straightforward, method of detecting the presence and determining the magnitude of puckering in substituted cyclobutane rings, and to ascertain whether the results could be interpreted in terms of an equilibrium between axial (I) and equatorial (II) conformations.