Intra-molecular hydrogen bonding with organic fluorine in the solution state: Deriving evidence by a two dimensional NMR experiment

The direct evidence for the existence of intra-molecular C–F⋯H–N hydrogen bond in organofluorine molecules, in the liquid state, is derived using NMR spectroscopy by the detection of long range interactions among fluorine, nitrogen and hydrogen atoms. The present study reports the determination of the relative signs and magnitudes of through space and through bond couplings to draw unambiguous evidence on the existence of weak molecular interactions involving organic fluorine. It is a simple, easy to implement, 15N natural abundant two dimensional heteronuclear 15N–1H double quantum-single quantum correlation experiment. The existence of intra-molecular hydrogen bond is conclusively established in the investigated molecules.