The X-Ray structures of four methyl a,B-diphenylacrylate derivatives were solved by direct methods from diffractometer data. (I) (Z)-methyl B-p-nitre phenyl-a-phenylacrylate, C16H13NOr, is monoclinic, P21/n, with a = 8.296(1), b = 6.703(2), c = 24.863(5)6, 6 = 96.25(1)', (Z)methyl a-p-nitrophenyl-6-phenylacrylate, C16H13N04, is triclinic, P 1 , with a = 14.:33(3), b = 10.048(2), c = 9.907(2)&, a = 80.75(1), B = 92.98(1), y = 92.48 ( 2 ) , v = 1395.6(5)A3, Z = 4. (111) (E)-methyl B-p-nitrophenyl-a-phenylacrylate, C I ~H ~~N O ~, is monoclinic, C c , with a = 5.819(2), b = 16.610(5), c = 14.843 (4)&, 6 = 96.14(2)', V = 1426.4(7)&', Z = 4. (IV) (E)-methyl 6-methyl-B-pnitrophenyl-a-phenylacrylate, C17H15N04, is monoclinic, P21/a, with a = 13.751 (4), b = 11.145(3), c = 10.956(4)A, 6 = 116.42(2)', V = 1503.7(8)A3, Z = 4. ester substituents are generally twisted out of the ethylenic bond mean plane to avoid steric hindrance : only phenyl a in molecule I1 and ester group in 111 are coplanar with the C=C bond. The C(arom.1-C=C bond angles are significantly greater than 120'. V = 1374.4(5)A3, Z = 4L (11) Molecular conformations are discussed and compared. The aromatic and n T a b l e a u 6. -Di8tanCeS interatomiques ( A ) ) -C ( 1 4 ) -C ( 1 3 ) C ( 5 ) -N ( 1 5 ) -0 ( 1 6 ) C ( 5 ) -N ( 1 5 ) -0 ( 1 7 ) C ( 1 2 ) -N ( 1 5 ) -0 (1 6 ) C ( 1 2 ) -N ( 1 5 ) -0 ( 1 7 ) 0 ( 1 6 ) -N (1 5 ) -0 ( 1 7 ) C ( l ) -C ( l S ) -0 ( 1 9 )