Investigation of Three Diasteromeric Chalcone Epoxides Derivatives by NMR Spectroscopy and X-ray Crystallography

Structures of diasteromeric chalcone epoxides derivatives [3-(4-nitrophenyl) oxiran-2-yl)(phenyl)]-methanone (C15H11NO4), compound 1; (3,4-dimethoxy phenyl)(3-(4-nitrophenyl)-oxiran-2-yl)methanone (C17H15NO6) compound 2 and [(3-(4-nitrophenyl)-oxiran-2-yl) phenyl-methanol] (C15H13NO4) compound 3 were established by spectral and X-ray diffraction studies. Compound 1 crystallizes in the monoclinic space group P2(1)/c with unit cell parameters a = 10.3127(10), b = 10.45331(10), c = 12.9227(13) angstrom, beta= 113.769(2)degrees, Z = 4. Compound 2 crystallizes in the triclinic space group P-1 with unit cell parameters a = 6.977(1), b = 8.259(1), c = 13.964(2) angstrom, alpha = 103.889(2), beta = 91.151(2), gamma = 100.780(2)degrees, Z = 2. Compound 3 crystallizes in the monoclinic space group P2(1) with unit cell parameters a = 6.708(1), b = 8.388(1), c = 12.407(2) angstrom, beta = 103.322(3)degrees, Z = 2. The absolute configurations of 3 for the chiral centers are 1S, 2R, and 3R. In structures 1 and 2, the molecules in the crystal are linked by C-H center dot center dot center dot O interactions and van der Waals forces. Molecules 2 in the crystal are stacked in an anti-parallel fashion along the a-axis by pi center dot center dot center dot pi interactions which gives additional support to molecular packing stability. In structure 3, the molecules in the crystal are linked by both intra- and intermolecular hydrogen bonds O1-H center dot center dot center dot O-2 and O1-H center dot center dot center dot O-4, respectively. Adjacent molecules are interconnected by intermolecular weak C-H center dot center dot center dot O interactions.