The crystal structure of ethylene carbonate

Abstract

The structure of crystalline ethylene carbonate has been determined by the X-ray method. The dimensions of the monoclinic unit cell, which contains four molecules of (CH2) ~. COs, are a ---8.92, b = 6.25, c = 6.94 A, fl = 100-5 °. The space group is C2/c. X-ray intensity data were obtained from Weissenberg moving-film photographs for all layers of the three principal axes, and structure amplitudes were deduced for 372 ~separate planes. The approximate structure was derived by means of Patterson F ~ syntheses, and refinement of atomic coordinates was achieved by successive three-dimensional Fourier syntheses. The five-membered dioxalan ring is not planar, but the molecule possesses a twofold axis of symmetry which coincides with the twofold axis of symmetry in the unit cell. Although the other bond lengths are approximately normal, those associated with the COa group are somewhat shorter than were expected, C ~-O being 1.15 _~ and C--O 1-33 A.