title: Inversion twinning in a second polymorph of the hydrochloride salt of the recreational drug ethylone.
abstract: A second polymorph of the hydrochloride salt of the recreational drug ethylone, C12H16NO3(+)·Cl(-), is reported [systematic name: (±)-2-ethylammonio-1-(3,4-methylenedioxyphenyl)propane-1-one chloride]. This polymorph, denoted form (A), appears in crystallizations performed above 308 K. The originally reported form (B) [Wood et al. (2015). Acta Cryst. C71, 32-38] crystallizes preferentially at room temperature. The conformations of the cations in the two forms differ by a 180° rotation about the C-C bond linking the side chain to the aromatic ring. Hydrogen bonding links the cations and anions in both forms into similar extended chains in which any one chain contains only a single enantiomer of the chiral cation, but the packing of the ions is different. In form (A), the aromatic rings of adjacent chains interleave, but pack equally well if neighbouring chains contain the same or opposite enantiomorph of the cation. The consequence of this is then near perfect inversion twinning in the structure. In form (B), neighbouring chains are always inverted, leading to a centrosymmetric space group. The question as to why the polymorphs crystallize at slightly different temperatures has been examined by density functional theory (DFT) and lattice energy calculations and a consideration of packing compactness. The free energy (ΔG) of the crystal lattice for polymorph (A) lies some 52 kJ mol(-1) above that of polymorph (B).
authors.affiliation: Department of Chemistry, Dalhousie University, PO Box 15000, Halifax, Nova Scotia, Canada B3H 4R2.
authors.forename: T Stanley
authors.initials: TS
authors.lastname: Cameron
authors.affiliation: Department of Chemistry, Dalhousie University, PO Box 15000, Halifax, Nova Scotia, Canada B3H 4R2.
authors.forename: J Stuart
authors.initials: JS
authors.lastname: Grossert
authors.affiliation: Science and Engineering Directorate, Canada Border Services Agency, 79 Bentley Avenue, Ottawa, Ontario, Canada K2E 6T7.
authors.forename: Chad R
authors.initials: CR
authors.lastname: Maheux
authors.affiliation: Science and Engineering Directorate, Canada Border Services Agency, 79 Bentley Avenue, Ottawa, Ontario, Canada K2E 6T7.
authors.forename: Idralyn Q
authors.initials: IQ
authors.lastname: Alarcon
authors.affiliation: Science and Engineering Directorate, Canada Border Services Agency, 79 Bentley Avenue, Ottawa, Ontario, Canada K2E 6T7.
authors.forename: Catherine R
authors.initials: CR
authors.lastname: Copeland
authors.affiliation: Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
authors.forename: Anthony
authors.initials: A
authors.lastname: Linden
mesh_terms: D000096:Acetone / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D003460:Crystallization; D018360:Crystallography, X-Ray; D005021:Ethylamines / Q000138:chemical synthesis* / Q000737:chemistry*; D006851:Hydrochloric Acid / Q000737:chemistry*; D006860:Hydrogen Bonding; D013287:Illicit Drugs / Q000138:chemical synthesis* / Q000737:chemistry*; D015394:Molecular Structure; D012492:Salts / Q000737:chemistry*
chemical_list: C000599434:2-ethylammonio-1-(3,4-methylenedioxyphenyl)propane-1-one chloride; D005021:Ethylamines; D013287:Illicit Drugs; D012492:Salts; D000096:Acetone; D006851:Hydrochloric Acid
keywords: DFT calculations; absolute structure refinement; amphetamine analogue; computational chemistry; crystal structure; ethylone; hydrochloride salt; hydrogen bonding; lattice energy calculations; pharmaceutical compound; polymorphism; twinning