The crystal structure of the diolefin of [2.2]paracyclophane

Abstract

and two molecules in the unit cell in space group P21/c. The structure has been refined by full matr ix three-dimensional least-squares methods, and the final parameters include small corrections for molecular libration. The aromatic rings are bent into a boat form about 14 ° at each end, and the bonds to the a-carbons are bent an additional 15 ° from the plane of the edge of each aromatic ring. The ring deformation may also be described as a folding of 16 ° about a line between the p-substituted atoms. The exocyclic single bond distance is 1.51/~, at least 0.02/~ longer than normal. The lengthening is at tr ibuted in par t to the orthogonality of the u-systems in the molecule and in part to intramolecular strain. Other distances are normal. The distribution of strain in the molecule is discussed.