Crystal structure of tramadol hydrochloride, C16H26NO2Cl

The crystal structure of tramadol hydrochloride has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional techniques. Tramadol hydrochloride crystallizes in space group Cc (#9) with a = 9.680 72(2), b = 19.191 27(4), c = 9.285 94(1)angstrom, beta = 100.5923(1)degrees, V = 1695.795(5)angstrom(3), and Z = 4. The solid-state conformation of the cation differs from the minimum-energy conformation of the tramadol cation in water, and from the conformation observed in the benzoic acid adduct of tramadol hydrochloride. N-H center dot center dot center dot Cl and O-H center dot center dot center dot Cl hydrogen bonds form a zigzag chain with graph set C1,2(8) along the c-axis. C-H center dot center dot center dot O hydrogen bonds also contribute to the crystal energy. The powder pattern has been submitted to ICDD for inclusion in the Powder Diffraction File T. (C) 2015 International Centre for Diffraction Data.