C-H ... PI(AR) ... CL-C, C-CL ... PI(AR), CL ... CL AND OTHER INTERACTIONS IN THE CRYSTAL-STRUCTURE OF 6-BENZOYL-2,4-BIS(TRICHLOROMETHYL)-1,3-BENZODIOXIN

The title compound is monoclinic, P2(1)/n, Z = 4, a = 9.934(1), b = 18 .399(2), c = 11.098(2)Angstrom, beta = 111.08(1)degrees. The molecule can conveniently be visualized as a benzophenone molecule with one of the aromatic rings fused to a 1,3-dioxin ring which adopts a distorted envelope conformation with cis-trichloromethyl groups substituted at positions 2 and 4. An interaction, observed for the first time, involv es a hydrogen atom and a chlorine atom from opposite sides of the same aromatic ring to give C-H...pi(Ar)...Cl-C. The parameters are H...rin g-centroid 2.63 Angstrom, Cl...ring centroid 3.41 Angstrom, H...ring-c entroid...Cl 167 degrees, C-H...ring centroid 159 degrees, C-Cl...ring centroid 150.2 degrees. The pi(Ar) system is that of the unfused arom atic ring. A second pi(Ar)...Cl-C interaction occurs but this time wit h the pi(Ar) system of the fused aromatic ring. The Cl...Cl and Cl...O (=C) interactions form the familiar zig-zag pattern which has been not ed for many chloroaromatic compounds.