title: Discriminating the structure of exo-2-aminonorbornane using nuclear quadrupole coupling interactions.
abstract: The intrinsic conformational and structural properties of the bicycle exo-2-aminonorbornane have been probed in a supersonic jet expansion using Fourier-transform microwave (FT-MW) spectroscopy and quantum chemical calculations. The rotational spectrum revealed two different conformers arising from the internal rotation of the amino group, exhibiting small (MHz) hyperfine patterns originated by the (14)N nuclear quadrupole coupling interaction. Complementary ab initio (MP2) and DFT (B3LYP and M05-2X) calculations provided comparative predictions for the structural properties, rotational and centrifugal distortion data, hyperfine parameters, and isomerization barriers. Due to the similarity of the rotational constants, the structural assignment of the observed rotamers and the calculation of the torsion angles of the amino group were based on the conformational dependence of the (14)N nuclear quadrupole coupling hyperfine tensor. In the most stable conformation (ss), the two amino N-H bonds are staggered with respect to the adjacent C-H bond. In the second conformer (st), only one of the N-H bonds is staggered and the other is trans. A third predicted conformer (ts) was not detected, consistent with a predicted conformational relaxation to conformer ss through a low barrier of 5.2 kJ mol(-1).
authors.affiliation: Departamento de Química Física, Facultad de Ciencia y Tecnología, Universidad del País Vasco (UPV-EHU), Ap. 644, 48080 Bilbao, Spain.
authors.forename: Patricia
authors.initials: P
authors.lastname: Écija
authors.forename: Emilio J
authors.initials: EJ
authors.lastname: Cocinero
authors.forename: Alberto
authors.initials: A
authors.lastname: Lesarri
authors.forename: Judith
authors.initials: J
authors.lastname: Millán
authors.forename: Francisco
authors.initials: F
authors.lastname: Basterretxea
authors.forename: José A
authors.initials: JA
authors.lastname: Fernández
authors.forename: Fernando
authors.initials: F
authors.lastname: Castaño