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+center dot C6H13N4+center dot 2C(7)H(3)ClNO(4)(-), (I), hexamethylenetetraminium hydrogen bis(2-chloro-4-nitrobenzoate), 0.5C(6)H(13)N(4)(+)center dot C7H3.50ClNO4-, (II), hexamethylenetetraminium 2-chloro-4-nitrobenzoate, C6H13N4+center dot C7H3ClNO4-, (IIIa) and (IIIb). All four molecular salts show N+-H center dot center dot center dot 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.