ROTATIONAL-ISOMERISM AND CRYSTAL-STRUCTURE OF 1,1'-DICYANO-1,1'-BICYCLOOCTYL

The dipole moment of 1,1'-dicyano-1,1'-bicyclooctyl (1) has been measu red in carbon tetrachloride and benzene over a range of temperatures. Analysis of the relative permittivity data shows that at 25 degrees C in carbon tetrachloride, the compound exists in 26% gauche and 74% tra ns. The experimentally derived values of the energy difference between the gauche and trans rotamers, the dihedral angle of the gauche rotam er and the gauche/trans population quotient are compared with values p redicted by molecular mechanics calculations. The crystal structure of (1) has also been determined by single-crystal X-ray diffraction meth ods. The molecule crystallizes in the triclinic space group P (1) over bar, a = 6.849(2) Angstrom, b = 7.065(3) Angstrom, c = 9.588(3) Angst rom, alpha = 90.82(3)degrees, beta = 105.42(2)degrees, gamma = 118.26( 2)degrees, V = 388.5(2) Angstrom(3), Z = 1. The molecule adopts the tr ans conformation in the crystalline state. (C) 1998 Elsevier Science B .V.