Unexpected Polymorphism in Nitroanilines

Abstract

We are currently engaged in a systematic study of solid forms, including polymorphs, co-crystals and salts, produced by simple organic molecules with weakly interacting functional groups. A Microvate[1] reaction block has been used to investigate the effects of temperature and solvent on crystallisation of polymorphs, co-crystals and salts. This allows various temperature profiles involving different rates of heating, cooling and stepped cooling to be used with a number of solvents. Slurry conversion techniques and sublimation can also be utilised. In one line of study we have attempted to make co-crystals and salts of substituted nitroanilines. In one of these experiments using 2-methyl-6-nitroaniline with organic acids we have unexpectedly obtained two as yet unreported forms of pure 2-methyl-6-nitroaniline. Form 1 crystallised in space group P21/c, a = 8.927Å, b = 11.186Å, c = 14.680Å, ? = 90°, ? = 104.79°, ? = 90° and Form 2 in space group P21/c, a = 3.925Å, b = 12.850Å, c = 14.275Å, ? = 90°, ? = 91.46°, ? = 90°. In light of these findings 2-methyl-3-nitroaniline has also been investigated and so far one pure form of the compound has been crystallised in space group P21, a = 14.012Å, b = 4.021Å, c = 15.483Å, ? = 90°, ? = 90°, ? = 90°. On the poster the structures of the crystal forms and the relationships between them will be assessed.
1. www.ReactArray.com

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