Electrical Polarization of Tetramethylcyclobutanes

Because the postulated non-planarity of sym-tetramethylcyclobutanedione is based on a small value of electrical polarization, the cis- and trans-2,2,4,4-tetramethylcyclobutane-1,3-diisocyanides have been prepared and stereospecifically rearranged to the analogous dicyanides. These substances show sufficiently large polarizations that the explanation of ring non-planarity is substantiated. Calculations in terms of the expected and observed dipole moments show that the ring deviates 20–30° from planarity. Although this non-planarity is not static, according to consideration of the cis geoisomers it would appear that one conformation is more prevalent than any others.