Acta Crystallographica Section B

Structural Science

Volume 55, Part 2 (April 1999)

research papers

Acta Cryst. (1999). B55, 209-215 [ doi:10.1107/S0108768198010349 ]

Experimental evidence for the amino-group non-planarity in nitroanilines: neutron diffraction study of 2-methyl-5-nitroaniline at 100 K

J. Ellena, A. E. Goeta, J. A. K. Howard, C. C. Wilson, J. C. Autino and G. Punte

Abstract: An appreciable degree of pyramidalization of the amine N atom is observed in the title compound. The existence of polar chains, induced by N-HO synthons, is confirmed. C-HO interactions, not noted in a previous X-ray study, were found to stabilize further the known head-to-tail assembling of the chains. The structure can be described as non-polar (101) layers, embodying chains interlinked by centrosymmetric dimers, connected by C(aryl)-H [pi] interactions. The latter are not present in m-nitroaniline, 2-methyl-4-nitroaniline and other related compounds with chains built from similar N-HO synthons and assembled head-to-head. This finding implies that an obvious relationship between molecular recognition patterns and crystal structures should not be assumed.