title: Quantum-chemical, NMR and X-ray diffraction studies on (+/-)-1-[3,4-(methylenedioxy)phenyl]-2-methylaminopropane.
abstract: Time-averaged conformations of (+/-)-1-[3,4-(methylenedioxy)phenyl]-2-methylaminopropane hydrochloride (MDMA, "ecstasy") in D(2)O, and of its free base and trifluoroacetate in CDCl(3), were deduced from their (1)H NMR spectra and used to calculate their conformer distribution. Their rotational potential energy surface (PES) was calculated at the RHF/6-31G(d,p), B3LYP/6-31G(d,p), B3LYP/cc-pVDZ and AM1 levels. Solvent effects were evaluated using the polarizable continuum model. The NMR and theoretical studies showed that, in the free base, the N-methyl group and the ring are preferentially trans. This preference is stronger in the salts and corresponds to the X-ray structure of the hydrochloride. However, the energy barriers separating these forms are very low. The X-ray diffraction crystal structures of the anhydrous salt and its monohydrate differed mainly in the trans or cis relationship of the N-methyl group to the alpha-methyl, although these two forms interconvert freely in solution.
authors.affiliation: Departamento de Química Inorgánica y Analítica, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Olivos 1007, Independencia, Santiago, Chile. gzapata@uchile.cl
authors.forename: Gerald
authors.initials: G
authors.lastname: Zapata-Torres
authors.forename: Bruce K
authors.initials: BK
authors.lastname: Cassels
authors.forename: Julia
authors.initials: J
authors.lastname: Parra-Mouchet
authors.forename: Yvonne P
authors.initials: YP
authors.lastname: Mascarenhas
authors.forename: Javier
authors.initials: J
authors.lastname: Ellena
authors.forename: A S
authors.initials: AS
authors.lastname: De Araujo
mesh_terms: D006213:Hallucinogens / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D008968:Molecular Conformation; D018817:N-Methyl-3,4-methylenedioxyamphetamine / Q000737:chemistry*; D011789:Quantum Theory; D014961:X-Ray Diffraction
chemical_list: D006213:Hallucinogens; D018817:N-Methyl-3,4-methylenedioxyamphetamine