Structural and computational analysis of published neutron diffraction data show that crystalline vitamin B12 coenzyme contains a strong intramolecular N-H...Ph hydrogen bond

Abstract

The neutron diffraction crystal structure of vitamin B12 coenzyme [Bouquiere et al. (1993). Acta Cryst. B49, 79–89] contains a yet unnoticed intramolecular aromatic hydrogen bond donated by a propionamide side chain and accepted by the benzimidazole group. The distance from the H-atom to the aromatic midpoint is only 2.58 Å and the bond energy is calculated to be 16.7 kJ mol−1.