Abstract

The conformation of a series of catecholamines and related compounds in solution has been studied by nuclear magnetic resonance spectroscopy. In molecules with a β-hydroxyl group, the preferred conformation is one in which the amino group is trans to the aromatic ring and gauche to the β-hydroxyl group; the fractional population of this rotamer is approximately 0.8. The major interaction leading to the predominance of this rotamer is shown to be an electrostatic or hydrogen bonding interaction between the amino and β-hydroxyl groups. Comparison of these results with theoretical calculations shows that extended Hückel theory calculations give only qualitative agreement, while with the method of perturbative configuration interaction using localised orbitals (PCILO) the agreement is much better.