Energetics of aminomethylpyrimidines: An examination of the aromaticity of nitrogen heteromonocyclic derivatives |
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| Institution: | 1. School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China;2. School of Environmental Science and Engineering, Tianjin University, Tianjin 300072, China;3. Tianjin Academy of Environmental Sciences, Tianjin 300191, China;4. School of Environmental and Chemical Engineering, Tianjin Polytechnic University, Tianjin 300387, China;1. Department of Biology, University of Pisa, 56127 Pisa, Italy;2. Laboratory of Nuclear Lipid BioPathology, Research Center of Biochemical-Specialized Analyses, 06100 Perugia, Italy |
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| Abstract: | The standard (po = 0.1 MPa) molar enthalpies of formation, in the gaseous phase, at the reference temperature of 298.15 K, of 2-amino-4-methylpyrimidine ((98.1 ± 1.6) kJ · mol?1), 2-amino-4,6-dimethylpyrimidine ((55.9 ± 1.8) kJ · mol?1) and 4-amino-2,6-dimethylpyrimidine ((60.1 ± 1.8) kJ · mol?1) were calculated from the enthalpies of formation, in the crystalline phase, and enthalpies of sublimation, derived, respectively, from static bomb combustion calorimetry and Knudsen effusion technique results. In order to quantify the resonance effects arising from the substitution on the pyrimidine ring, hypothetical isodesmic reactions were used to analyze the experimental gaseous-phase enthalpies of formation. The aromaticity of benzene, pyridine, pyrimidine and the substituted pyrimidines was investigated in terms of magnetic (NICS), geometric (HOMA), electronic (Shannon aromaticity, QTAIMs ring critical point properties and HOMO–LUMO gap), reactive (hardness), vibrational (Kekulé mode) and spectroscopic (UV–Vis) properties. |
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| Keywords: | Pyrimidines Aromaticity Experimental molecular energetics UV–Vis QTAIM Kekulé mode |
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