The crystal structure of and twinning in γ-o-nitroaniline

Abstract

to the (100) plane and passing through the point (0,~,-~). The presence of the pseudo axis explains the occurrence of twinning in the crystals as well as the presence of diffuse streaks in some of the Weissenberg photographs.

Polymorphism of 2-nitroaniline studied by calorimetric (DSC), structural (X-ray diffraction) and spectroscopic (FT-IR, Raman, UV–Vis) methods

“…They are very similar to the following for the c phase: a = 15.45(2); b = 10.01(2); c = 8.57(1) Å and b = 107.4(2)°in the monoclinic space group P2 1 /a with 8 molecules in the unit cell [1]. The P2 1 /n space group was chosen for the b phase in order to fulfil the crystallographic requirement of b angle value larger than 90°in monoclinic system [35] what implicated mutually exchanged the a-and c-axes in the space groups of both forms.…”

“…Until now, only the centrosymmetric c-o-NA structure has been solved [1]. O-NA has been recently found to be the chromophore in 5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile (ROY) crystallizing as 10 polymorphs of different colours (red, orange, yellow) [5][6][7][8].…”

“…The most investigated p-nitroaniline (p-NA) acts as model compound of D-p-A system due to intramolecular charge transfer (ICT) between the electron donor -NH 2 group and the electron withdrawing -NO 2 group through the phenyl ring. Contrary to p-NA and m-NA, the o-NA molecules form easily the intramolecular N-HÁ Á ÁO hydrogen bondings (intra H-bonds) [1].…”

A 2:1 complex of 2,4-dinitroaniline and 1,4,7,10,13,16-hexaoxacyclooctadecane (18-crown-6)

“…Dihedral angles between the phenyl plane and the oand p-nitro groups [4.8 (5) and 1.3 (4) ° respectively] correspond to short C-N distances of 1.443 (7) and 1.450 (7)/~ (Kawai, Kashino & Haisa, 1976). The less accurately determined rotation of the amino group [8.3 (7) ° ] is smaller than in o-nitroaniline (Dhaneshwar, Tavale & Pant, 1978); the short C(10)-N(16) bond [1.326 (7)A] and lengthened adjacent C-C bonds in the ring (1.416A) fit the correlation reported for primary aromatic amines (Holden, Dickinson & Bock, 1972). Thus the approximate coplanarity and, especially, the distribution of bond distances in 2,4-dinitroaniline indicate considerable quinonoid contributions to the overall resonance state of the molecule.…”

“…The resulting increased acidity of the amino group probably facilitates the formation of bifurcated hydrogen bridges (Table 5) (Dhaneshwar et al, 1978) and in the 1:2 adduct of 18-crown-6 and (2,4-dinitrophenyl)hydrazine (Hilgenfeld & Saenger, 1981). Comparing the latter structure to the current one, many analogies can be detected such as the overall arrangement of the molecules (including the inversion centre), interactions with all O atoms, bifurcation of hydrogen bridges and stacking in the lattice (Fig.…”