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Title: 5-Methylhydantoin: from Isolated Molecules in a Low-Temperature Argon Matrix to Solid State Polymorphs Characterization
Authors: Nogueira, Bernardo Albuquerque 
Ildiz, Gulce O
Lage, João Carlos Canotilho 
Eusébio, Maria Ermelinda da Silva 
Henriques, Marta Sofia C
Paixao, Jose A
Fausto, Rui 
Issue Date: 2017
Volume: 121
Issue: 28
Abstract: 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 σ and π 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.
ISSN: 1089-5639
DOI: 10.1021/acs.jpca.7b05030
Rights: openAccess
Appears in Collections:I&D CQC - Artigos em Revistas Internacionais

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