The crystal structure of meta-dinitrobenzene

The crystal of meta-dinitrobenzene, C6H 4(N 02)2> is orthorhombic pyram idal. The dimensions of the un it cell, which contains 4 molecules, are a = 13-3A, 6 = 14*1 A, c = 3-80A and the space group is Pbn. The m ethod of double Fourier series has been applied, and a projection of the electron density on the ab plane has been made. The plane of the benzene ring of the molecule is inclined a t an angle of 20° to the 6-axis, and is parallel to the a-axis. W ithin the limits of experiment, the benzene ring is a regular hexagon of side 1-41 A. The C—N links do not lie in the plane of the ring, bu t make an angle of 15° w ith it. The C-N distance is 1*54A, the N -0 distances have been assumed the same, 1*20A, and the 0 -0 distance is 2* 17 A. The closest approach of O to CH in adjacent molecules is about 3*0A, th a t between O and O about 3-2 A, and th a t between CH and CH is 3*8 A. A discussion of the packing of the molecules in the structure is given.