title: The structure of pyrazoles in the solid state: a combined CPMAS, NMR, and crystallographic study.
abstract: The structures of six N-unsubstituted pyrazoles, three already known and three newly synthesized, have been studied by a combination of X-ray crystallography, multinuclear NMR (solution and solid state), and density functional theory (DFT) calculations. In those cases where crystal structure and CPMAS NMR were available, the agreement was almost perfect, allowing a prediction of the tautomer (with certitude) and the tetrameric structure (with high probability) in the case of 5-isopropyl-3-phenyl-1H-pyrazole without knowing the X-ray structure. In the case of the 5-(2-benzylphenyl)-3-trifluoromethyl-1H-pyrazole above represented, the DFT calculations at the B3LYP/6-31G level justify the great stability of this tautomer by the presence of an intramolecular N-H...pi interaction, present in solution.
authors.affiliation: Departamento de Química Organica y Bio-Organica, Facultad de Ciencias, UNED, Senda del Rey 9, E-28040 Madrid, Spain. rclaramunt@ccia.uned.es
authors.forename: Rosa M
authors.initials: RM
authors.lastname: Claramunt
authors.forename: Pilar
authors.initials: P
authors.lastname: Cornago
authors.forename: Verónica
authors.initials: V
authors.lastname: Torres
authors.forename: Elena
authors.initials: E
authors.lastname: Pinilla
authors.forename: M Rosario
authors.initials: MR
authors.lastname: Torres
authors.forename: André
authors.initials: A
authors.lastname: Samat
authors.forename: Vladimir
authors.initials: V
authors.lastname: Lokshin
authors.forename: Magali
authors.initials: M
authors.lastname: Valés
authors.forename: José
authors.initials: J
authors.lastname: Elguero
mesh_terms: D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008958:Models, Molecular; D015394:Molecular Structure; D011720:Pyrazoles / Q000737:chemistry*; D012996:Solutions
chemical_list: D011720:Pyrazoles; D012996:Solutions