The molecular structure of trimethylenecyclopropane

Abstract The molecular structure of trimethylenecyclopropane has been determined from electron diffraction data obtained on the vapor. Planarity of the molecule was assumed and shrinkages were calculated from the evaluated non-bonded CC distances. The geometric parameters calculated by least squares from the molecular intensity [qM(q)] are: The calculated shrinkges are: δ C 1 C 6 = 0.009 A; δ C 2 C 6 = 0.028 A. The uncertainties quoted for the distances are twice the calculated standard deviations. A variation of Walsh's model for the bonding in cyclopropane is proposed, to account for reported differences in bond lengths between trimethylenecyclopropane and several related molecules. The structural data suggest that delocalization is present in these 3-member rings.