Crystal structure of tramadol hydrochloride, C16H26NO2Cl

Abstract

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 groupCc(#9) witha= 9.680 72(2),b= 19.191 27(4),c= 9.285 94(1) Å,β= 100.5923(1)°,V= 1695.795(5) Å3, andZ= 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···Cl and O–H···Cl hydrogen bonds form a zigzag chain with graph setC1,2(8) along thec-axis. C–H···O hydrogen bonds also contribute to the crystal energy. The powder pattern has been submitted to ICDD for inclusion in the Powder Diffraction File™.