Stoichiometric and polymorphic salts of hexamethylenetetraminium and 2-chloro-4-nitrobenzoate
Four molecular salts made from hexamethylenetetraminium and 2-chloro-4-nitrobenzoate have been synthesized and are reported, namely ammonium hexamethylenetetraminium bis(2-chloro-4-nitrobenzoate), NH4+·C6H13N4+·2C7H3ClNO4−, (I), hexamethylenetetraminium hydrogen bis(2-chloro-4-nitrobenzoate), 0.5C6H13N4+·C7H3.50ClNO4−, (II), hexamethylenetetraminium 2-chloro-4-nitrobenzoate, C6H13N4+·C7H3ClNO4−, (IIIa) and (IIIb). All four molecular salts show N+—H...O− hydrogen bonding. Salt (I) crystallized out with an NH4+ counter-ion which came from decomposition of 50% of the hexamethylenetetraminium cation in solution. (II) shows an unusual asymmetric unit, with both a hexamethylenetetraminium cation and a partially deprotonated 2-chloro-4-nitrobenzoate anion. Salts (IIIa) and (IIIb) are polymorphs of each other. This work shows that hexamethylenetetramine only protonates once, even in the presence of excess acid.
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Document Type: Research Article
Affiliations: Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Private Bag, PO WITS, 2050, Johannesburg, South Africa
Publication date: January 1, 2017