Thermodynamic stability of 2,4,6-tris(nitromethyl)-1,3,5-triazine: an experimental and theoretical study |
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Authors: | A V Shastin V L Korolev T S Pivina T I Godovikova B L Korsunskii P A Belyakov N I Golovina G V Shilov |
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Institution: | 1.Institute of Problems of Chemical Physics,Russian Academy of Sciences,Chernogolovka, Moscow Region,Russian Federation;2.N. D. Zelinsky Institute of Organic Chemistry,Russian Academy of Sciences,Moscow,Russian Federation |
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Abstract: | The molecular geometries and electronic structures of 2,4,6-tris(nitromethyl)-1,3,5-triazine isomers were investigated by
the density functional method DFT/B3LYP/6-311++G** to elucidate the structural factors responsible for the stability of these
systems. It was shown that a characteristic feature of the nitromethyl tautomer (1) of 2,4,6-tris (nitromethyl)-1,3,5-triazine consists in nonvalence interactions between an oxygen atom of nitro group and
a carbon atom of triazine ring, which are probably due to Coulomb attraction between them. The tautomer with the 2,4,6-tris
(nitromethylene)-hexahyrdo-1,3,5-triazine structure (2) is stabilized trough direct polar conjugation between the amino and nitro groups at the double bond. Structural strain of
the molecule with the 2,4,6-tris(aci-nitromethyl)-1,3,5-triazine structure (3) is the reason for its thermodynamic instability. X-ray data indicate that the compound under study exists in the triazine
tautomeric form 1 and the distances between oxygen atoms of nitro group and carbon atom of the triazine ring are shortened. NMR data suggest
the existence of triazine in the nitromethyl form 1 in acetonitrile and acetone and a tautomeric equilibrium between the nitromethyl and nitromethylene forms in a more polar
solvent (DMSO). The results obtained suggest a Coulomb-type stabilization of the 2,4,6-tris(nitromethyl)-1,3,5-triazine molecule
in the gas phase, in the crystal, and in nonpolar solvents. |
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