14N Quadrupole Resonance Study of a Hydrogen Bond: Hexamethylenetetramine Triphenol

The nuclear quadrupole resonance spectrum of hydrogen bonded hexamethylenetetramine triphenol was observed at 77°K and at room temperature. The absorption lines were assigned to two inequivalent nitrogen sites. N(1), which is not hydrogen bonded, gave e2qQ/h=4665.7 kHz and η=0 at 77°K. N(2), which takes part in an N···H–O hydrogen bond, has e2qQ/h=4208.1 kHz and η=0.05014 also at 77°K. By comparing these data with the spectrum of pure hexamethylenetetramine (HMT) the effects of the hydrogen bond on the HMT nitrogen sites could be obtained. It is concluded that the nitrogen site N(2) loses a few hundredths of an electron from its lone pair orbital as a result of the hydrogen bond interaction.