An investigation to elucidate the factors dictating the crystal structure of seven ammonium carboxyl­ate mol­ecular salts

The crystal structures of seven ammonium carboxyl­ate salts are reported, namely (RS)-1-phenyl­ethan-1-aminium isonicotinate, C(8)H(12)N(+)·C(6)H(4)N(1)O(2) (−), (I), (RS)-1-phenyl­ethan-1-aminium flurbiprofenate [or 2-(3-fluoro-4-phenyl­phen­yl)propano­ate], C(8)H(12)N(+)·C(15)H(12)FO(2) (−), (II), (RS)-1-phenyl­ethan-1-aminium 2-chloro-4-nitro­benzoate, C(8)H(12)N(+)·C(7)H(3)ClNO(4) (−), (III), (RS)-1-phenyl­ethan-1-aminium 4-iodo­benzoate, C(8)H(12)N(+)·C(7)H(4)IO(2) (−), (IV), (S)-1-cyclo­hexyl­ethan-1-aminium 2-chloro-4-nitro­benzoate, C(8)H(18)N(+)·C(7)H(3)ClNO(4) (−), (V), 2-(cyclo­hex-1-en-1-yl)ethan-1-aminium 4-bromo­benzoate, C(8)H(16)N(+)·C(7)H(4)BrO(2) (−), (VI), and (S)-1-cyclo­hexyl­ethan-1-aminium 4-bromo­benzoate, C(8)H(18)N(+)·C(7)H(4)BrO(2) (−), (VII). Salts (II) to (VII) feature three N(+)—H⋯O(−) hydrogen bonds, which form one-dimensional hydrogen-bonded ladders. Salts (II), (III), (IV), (V) and (VII) have a type II ladder system despite the presence of halogen bonding and other inter­molecular inter­actions, whereas (VI) has a type III ladder system. Salt (I) has a unique hydrogen-bonded system of ladders, featuring both N(+)—H⋯O(−) and N(+)—H⋯N hydrogen bonds owing to the presence of the pyridine functional group. The presence of an additional hydrogen-bond acceptor on the carboxyl­ate cation disrupts the formation of the ubiquitous type II and III ladder found predominately in ammonium carboxyl­ate salts. Halogen bonding, however, has no influence on their formation.