title: An experimental and theoretical NMR study of NH-benzimidazoles in solution and in the solid state: proton transfer and tautomerism.
abstract: This paper reports the (1)H, (13)C and (15)N NMR experimental study of five benzimidazoles in solution and in the solid state ((13)C and (15)N CPMAS NMR) as well as the theoretically calculated (GIAO/DFT) chemical shifts. We have assigned unambiguously the "tautomeric positions" (C3a/C7a, C4/C7 and C5/C6) of NH-benzimidazoles that, in some solvents and in the solid state, appear different (blocked tautomerism). In the case of 1H-benzimidazole itself we have measured the prototropic rate in HMPA-d 18.
authors.affiliation: Departamento de Química Orgánica y Bio-Orgánica, Facultad de Ciencias, UNED Senda del Rey 9, E-28040 Madrid, Spain.
authors.forename: Carla I
authors.initials: CI
authors.lastname: Nieto
authors.affiliation: Departamento de Química Orgánica y Bio-Orgánica, Facultad de Ciencias, UNED Senda del Rey 9, E-28040 Madrid, Spain.
authors.forename: Pilar
authors.initials: P
authors.lastname: Cabildo
authors.affiliation: Departamento de Química Orgánica y Bio-Orgánica, Facultad de Ciencias, UNED Senda del Rey 9, E-28040 Madrid, Spain.
authors.forename: M Ángeles
authors.initials: MÁ
authors.lastname: García
authors.affiliation: Departamento de Química Orgánica y Bio-Orgánica, Facultad de Ciencias, UNED Senda del Rey 9, E-28040 Madrid, Spain.
authors.forename: Rosa M
authors.initials: RM
authors.lastname: Claramunt
authors.affiliation: Instituto de Química Médica, CSIC, Juan de la Cierva, 3, E-28006 Madrid, Spain.
authors.forename: Ibon
authors.initials: I
authors.lastname: Alkorta
authors.affiliation: Instituto de Química Médica, CSIC, Juan de la Cierva, 3, E-28006 Madrid, Spain.
authors.forename: José
authors.initials: J
authors.lastname: Elguero
keywords: CPMAS; DNMR; GIAO; proton transfer; tautomerism