Étude Structurale Des Stilbènes III. Structures Par Diffraction de Rayons X de Quatre Dérivés E ou Z de L'α, β-Diphénylacrylate de Méthyle

The X-Ray structures of four methyl α, β-diphenylacrylate derivatives were solved by direct methods from diffractometer data. (I) (Z)-methyl β-p-nitrophenyl-α-phenylacrylate, C16H13NO4, is monoclinic, P21/n, with α=8.296 (1), b=6.703(2), c=24.863(5)A, β=96.25(1)°, V=1374.4(5)A3, Z=4, (II) (Z)-methyl α-p-nitrophenyl-β-phenylacrylate, C16H13NO4, is triclinic, P1, with α=14.233(3), b=10.048(2), c=9.907(2)A, α=80.75(1), β=92.98(1), γ=92.48(2)°, V=1395.6(5)A3, Z=4. (III) (E)-methyl β-p-nitrophenyl-α-phenylacrylate, C16H13NO4, is monoclinic, Cc, with α=5.819(2), b=16.610(5), c=14.843(4)A, β=96.14(2)°, V=1426.4(7)A3, Z=4. (IV) (E)-methyl β-methyl-β-p-nitrophenyl-α-phenylacrylate, C17H15NO4, is monoclinic, P21/α, with α=13.751 (4), b=11.145(3), c=10.956(4)A, β=116.42(2)°, V=1503.7(8)A3, Z=4. Molecular conformations are discussed and compared. The aromatic and ester substituents are generally twisted out of the ethylenic bond mean plane to avoid steric hindrance; only phenyl α in molecule II and ester group in III are coplanar with the CC bond. The C (arom.)-CC bond angles are significantly greater than 120°.