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), NH(4) (+)·C(6)H(13)N(4) (+)·2C(7)H(3)ClNO(4) (−), (I), hexa­methyl­ene­tetra­minium hydrogen bis­(2-chloro-4-nitro­benzoate), 0.5C(6)H(13)N(4) (+)·C(7)H(3.50)ClNO(4) (−), (II), hexa­methyl­ene­tetra­minium 2-chloro-4-nitro­benzoate, C(6)H(13)N(4) (+)·C(7)H(3)ClNO(4) (−), (IIIa) and (IIIb). All four mol­ecular salts show N(+)—H⋯O(−) hydrogen bonding. Salt (I) crystallized out with an NH(4) (+) 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.