Tramadol hydro­chloride–benzoic acid (1/1)

In the cation of the title co-crystal salt {systematic name: [2-hydroxy-2-(3-meth­oxy­phen­yl)cyclo­hexyl­meth­yl]dimethyl­aza­nium chloride–benzoic acid (1/1)}, C(16)H(31)NO(2) (+)·Cl(−)·C(7)H(6)O(2), 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.