Molecular and crystal structures of 1R,4R-cis-2-(4-phenylbenzylidene)-n-menthan-3-one

The molecular and crystal structures of chiral 1R,4R-cis-2-(4-phenylbenzyli dene)-n-menthan-3-one (I) have been determined by X-ray diffraction analysi s. Crystals I are monoclinic, a = 6.755(3) Angstrom, b = 9.860(3) Angstrom, c = 14.103(6) Angstrom, beta = 98.95(1)degrees, space group P2(1), Z = 2, and R = 0.035 for 1031 reflections. A chair conformation of the cyclohexano ne ring in the molecule is substantially distorted toward a "half-chair" co nformation. The enone and benzylidene groupings are virtually planar (the t orsion angles are equal to 13.0 degrees and 4.9 degrees respectively). The benzene rings of the biphenyl fragment are rotated with respect to each oth er through an angle of 40 degrees -43 degrees. Among the compounds under co nsideration, the distortion of bond angles at the sp(2) carbon atoms of the benzylidene grouping as a criterion for the steric stress of molecules is maximum in structure I. (C) 2001 MAIK "Nauka/Interperiodica".