2-Hydroxy-N-m-tolyl-acetamide: Optic spectroscopy, X-ray Crystallography and DFT study

The subject of our study is 2-hydroxy-N-m-tolylacetamide (HTA), which is theoretically characterized by the amide-imidol tautomerism. The molecular and crystal structure of HTA was confirmed by X-ray diffraction analysis, and intermolecular hydrogen bonds were found in its crystal structure due to the formation of dimer form of the amide tautomer. We investigated the possibility of HTA existing in tautomeric forms using IR, UV-visible spectroscopy, as well as DFT calculations of its neutral form in the gas phase and in chloroform using the CPCM algorithm. The monomer of HTA in the amide and imidol forms was fully optimized using the DFT/6-311G(d,p) method to determine the optimal tautomeric forms and calculate the Gibbs free energies and equilibrium constants. In addition, theoretical UV and IR spectra were calculated to find key absorption bands confirming a particular tautomer. However, we were unable to capture the absorption bands responsible for the tautomeric forms in the UV and IR spectra. The stability of the amide form relative to the imidol form was determined based on the DFT calculations. The DFT calculations clearly show the existence of the amide-imidol tautomers in solution.