RESUMO
N,N'-diethyl-4-nitrobenzene-1,3-diamine, C(10)H(15)N(3)O(2), (I), crystallizes with two independent molecules in the asymmetric unit, both of which are nearly planar. The molecules differ in the conformation of the ethylamine group trans to the nitro group. Both molecules contain intramolecular N-H...O hydrogen bonds between the adjacent amine and nitro groups and are linked into one-dimensional chains by intermolecular N-H...O hydrogen bonds. The chains are organized in layers parallel to (101) with separations of ca 3.4 A between adjacent sheets. The packing is quite different from what was observed in isomeric 1,3-bis(ethylamino)-2-nitrobenzene. 2,6-Bis(ethylamino)-3-nitrobenzonitrile, C(11)H(14)N(4)O(2), (II), differs from (I) only in the presence of the nitrile functionality between the two ethylamine groups. Compound (II) crystallizes with one unique molecule in the asymmetric unit. In contrast with (I), one of the ethylamine groups, which is disordered over two sites with occupancies of 0.75 and 0.25, is positioned so that the methyl group is directed out of the plane of the ring by approximately 85 degrees. This ethylamine group forms an intramolecular N-H...O hydrogen bond with the adjacent nitro group. The packing in (II) is very different from that in (I). Molecules of (II) are linked by both intermolecular amine-nitro N-H...O and amine-nitrile N-H...N hydrogen bonds into a two-dimensional network in the (10 2) plane. Alternating molecules are approximately orthogonal to one another, indicating that pi-pi interactions are not a significant factor in the packing. Bis(4-ethylamino-3-nitrophenyl) sulfone, C(16)H(18)N(4)O(6)S, (III), contains the same ortho nitro/ethylamine pairing as in (I), with the position para to the nitro group occupied by the sulfone instead of a second ethylamine group. Each 4-ethylamino-3-nitrobenzene moiety is nearly planar and contains the typical intramolecular N-H...O hydrogen bond. Due to the tetrahedral geometry about the S atom, the molecules of (III) adopt an overall V shape. There are no intermolecular amine-nitro hydrogen bonds. Rather, each amine H atom has a long (H...O ca 2.8 A) interaction with one of the sulfone O atoms. Molecules of (III) are thus linked by amine-sulfone N-H...O hydrogen bonds into zigzag double chains running along [001]. Taken together, these structures demonstrate that small changes in the functionalization of ethylamine-nitroarenes cause significant differences in the intermolecular interactions and packing.
