Stoichiometric and polymorphic salts of hexa-methyl-ene-tetra-minium and 2-chloro-4-nitro-benzoate.

Four mol-ecular salts made from hexa-methyl-ene-tetra-minium and 2-chloro-4-nitro-benzoate have been synthesized and are reported, namely ammonium hexa-methyl-ene-tetra-minium bis-(2-chloro-4-nitro-benzoate), NH4+·C6H13N4+·2C7H3ClNO4-, (I), hexa-methyl-ene-tetra-minium hydrogen bis-(2-chloro-4-nitro-benzoate), 0.5C6H13N4+·C7H3.50ClNO4-, (II), hexa-methyl-ene-tetra-minium 2-chloro-4-nitro-benzoate, C6H13N4+·C7H3ClNO4-, (IIIa) and (IIIb). All four mol-ecular salts show N+-H⋯O- hydrogen bonding. Salt (I) crystallized out with an NH4+ counter-ion which came from decomposition of 50% of the hexa-methyl-ene-tetra-minium cation in solution. (II) shows an unusual asymmetric unit, with both a hexa-methyl-ene-tetra-minium cation and a partially deproton-ated 2-chloro-4-nitro-benzoate 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.