Exposing Hidden Conformations of Carbamazepine Appearing Due to Interaction With the Solid Phase by 2D ¹H-¹⁵N HMBC NMR Spectroscopy

Abstract

Two-dimensional 1H-15N HMBC NMR spectra of the well-known anticonvulsant carbamazepine dissolved in different organic solvents, recorded on an NMR spectrometer prove the existence of hidden conformers in saturated solutions. Obtained conformer distribution arises due to the presence of the solid phase in saturated solution. A weak influence of ring currents was revealed for different molecular conformations of carbamazepine dissolved in a saturated solution, which provides a simple approach to discovering hidden conformations. Hidden conformers were found in three different solvents: dimethyl sulfoxide, chloroform, and dichloromethane.