Conformational studies on a 1,2,3,4,5-pentachloro-8-phenyltetralin

Abstract

The structure of r-1,t-2,c-3,t-4,5-pentachloro-8-phenyltetralin has been determined from single-crystal X-ray analysis by direct methods. The crystal data for the title compound are a= 9.600(5), b= 13.647(7), c= 12.132(6)Å, β= 90.1(1)°, monoclinic, space group P2₁/c, Z= 4. Full-matrix least-squares refinement based on 1 075 reflections with intensities I > 2σ(I) converged to R 0.044. Both aromatic rings are planar, within experimental error; the angle between the two best mean planes C(1)–C(10)(fused benzene and alicyclic ring) and C(11)–C(16)(phenyl ring) is 61.6°, resulting in a remarkable decrease of conjugation between the two aromatic systems. The alicyclic moiety of the molecule assumes a half-chair conformation, with the four chlorine atoms in axial and pseudoaxial positions. The above results, together with those inferred from ¹H n.m.r. and chemical methods, indicate the identical conformational preference of the title compound in both the solid state and in solution.