Publication: 5-Methylhydantoin: from isolated molecules in a low-temperature argon matrix to solid state polymorphs characterization
Nogueira, Bernardo A.
Öğrüç Ildız, Gülce
Eusebio, M. E. S.
Henriques, M. S. C.
Paixao, J. A.
Amer Chemical Soc, 1155 16th St, Nw, Washington, Dc 20036 USA
The molecular structure, vibrational spectra and photochemistry of 5-methylhydantoin (C4H6N2O2; 5-MH) were studied by matrix isolation infrared spectroscopy and theoretical calculations at the DFT(B3LYP)/6-311++G(d,p) theory level. The natural bond orbital (NBO) analysis approach was used to study in detail the electronic structure of the minimum energy structure of 5-MH, namely the specific characteristics of the sigma and pi electronic systems of the molecule and the stabilizing orbital interactions. UV irradiation of 5-MH isolated in argon matrix resulted in its photofragmentation through a single photochemical pathway, yielding isocyanic acid, ethanimine, and carbon monoxide, thus following a pattern already observed before for the parent hydantoin and 1-methylhydantoin molecules. The investigation of the thermal properties of 5-MH was undertaken by differential scanning calorimetry (DSC), polarized light thermal microscopy (PLTM) and Raman spectroscopy. Four different polymorphs of 5-MH were identified. The crystal structure of one of the polymorphs, for which it was possible to grow up suitable crystals, was determined by X-ray diffraction (XRD). Two of the additional polymorphs were characterized by powder XRD, which confirmed the molecules pack in different crystallographic arrangements.
Crystal-Structures, Infrared-Spectra, Hydantoins, Photochemistry, Derivatives, Inhibitors, Density