Tramadol hydrochloride–benzoic acid (1/1)

Abstract

In the cation of the title co-crystal salt {systematic name: [2-hydroxy-2-(3-methoxyphenyl)cyclohexylmethyl]dimethylazanium chloride–benzoic acid (1/1)}, C16H31NO2+·Cl−·C7H6O2, the N atom is protonated and the six-membered cyclohexane ring adopts a slightly distorted chair conformation. The dihedral angle between the mean planes of the benzene rings in the cation and the benzoic acid molecule is 75.5 (9)°. The crystal packing is stabilized by weak intermolecular O—H...Cl, N—H...Cl and C—H...π interactions, forming a two-dimensional chain network along the b axis. The benzoic acid molecule is not involved in the usual head-to-tail dimer bonding, but instead is linked to the ammonium cation through mutual hydrogen-bonding interactions with the chloride anion.