title: A facile method to determine the absolute structure of achiral molecules: supramolecular-tilt structures.
abstract: Achiral compounds 4-methoxy-4-(p-methoxyphenyl)cyclohexanoneethylene ketal (2), 4-hydroxy-4-(p-methoxy phenyl)cyclohexanoneethylene ketal (3), and 3,5-dimethyl-4-nitropyrazole (4) crystallized in chiral structures and the samples showed an enantiomeric excess. We have determined the absolute structures of these compounds by using X-ray diffraction with copper radiation at low temperatures. Moreover, we have also established the prevalent absolute structures in these samples, by comparing their calculated and solid-state vibrational circular dichroism (VCD) spectra. The consistency of this method was confirmed by using (R,R)-2,8-diiodo-4,10-dimethyl-6 H,12H-5,11-methano-dibenzo[b,f][1,5]diazocine, Tröger's base, (R,R)-1, as a chiral compound of known absolute configuration.
authors: Centro Universitario de la Defensa, Academia General Militar, 50090 Zaragoza, Spain.
authors: Rosa María
authors: RM
authors: Tejedor
authors: Santiago
authors: S
authors: Uriel
authors: Sara
authors: S
authors: Graus
authors: Teresa
authors: T
authors: Sierra
authors: José Luis
authors: JL
authors: Serrano
authors: Rosa M
authors: RM
authors: Claramunt
authors: Concepción
authors: C
authors: López
authors: Marta
authors: M
authors: Pérez-Torralba
authors: Ibon
authors: I
authors: Alkorta
authors: José
authors: J
authors: Elguero
mesh_terms: D002942:Circular Dichroism; D003512:Cyclohexanones / Q000737:chemistry*; D015394:Molecular Structure; D011720:Pyrazoles / Q000737:chemistry*; D013237:Stereoisomerism; D014961:X-Ray Diffraction / Q000295:instrumentation*
chemical_list: C585396:3,5-dimethyl-4-nitropyrazole; C585395:4-hydroxy-4-(p-methoxy phenyl)cyclohexanoneethylene ketal; C585394:4-methoxy-4-(p-methoxyphenyl)cyclohexanoneethylene ketal; D003512:Cyclohexanones; D011720:Pyrazoles