title: Can we predict the conformational preference of amides?
abstract: To what extent, if any, is the conformation of secondary amides revealed by theory? This question has now been addressed by computational methods using calculations at the B3LYP/6-31G level of theory and (1)H NMR spectroscopy. Both gas-phase and solvent studies predict a Z-anti conformation to be the lowest in energy for an evaluated series of acetamides. Moreover, Z-anti conformations may also be inferred from the chemical shifts of the N-CH alpha protons determined by NMR spectroscopy. Thus, a proton situated anti to the N-H proton consistently appears approximately 0.8 ppm further downfield than a proton situated gauche to the N-H proton. This finding, which could only be derived by using the DFT calculations of conformational preference as a guide to interpret the NMR data, might prove to be useful as a simple and convenient methodology for establishing amide conformation experimentally.
authors.affiliation: Departamento de Química Orgánica, Facultad de Ciencias, Universidad de Extremadura, E-06071 Badajoz, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Avalos
authors.forename: R
authors.initials: R
authors.lastname: Babiano
authors.forename: J L
authors.initials: JL
authors.lastname: Barneto
authors.forename: J L
authors.initials: JL
authors.lastname: Bravo
authors.forename: P
authors.initials: P
authors.lastname: Cintas
authors.forename: J L
authors.initials: JL
authors.lastname: Jiménez
authors.forename: J C
authors.initials: JC
authors.lastname: Palacios