Crystal structure of benzocyclobutene-1,2-dione

Abstract

Crystals of benzocyclobutene-1,2-dione (C₈H₄O₂) are orthorhombic, a= 7·938, b= 10·741, c= 7·135 Å, Z= 4, space group Pbc2₁. The structure was determined, with visually estimated Weissenberg data (Cu-K_α radiation), from a three-dimensional sharpened Patterson function, and full-matrix least-squares refinement reduced R to 0·080 for 432 observed reflexions. A concurrent application of direct methods to the centrosymmetric [001] projection yielded an identical solution. The two rings are planar, but the molecule as a whole is very slightly bowed. There are significant angular distortions in the benzene ring owing to the strain introduced by fusion to a four-membered ring. The packing arrangement is totally determined by van der Waals interactions.