Tautomerism of pyrimidyl-2-methane derivatives: medium effects, thermodynamics, kinetics and mechanism

Lapachev, V. V.; Zagulyaeva, O. A.; Petrenko, O. P.; Bichkov, S.F.; Mamatyuk, V. I.; Mamaev, V. P.

doi:10.1016/s0040-4020(01)96729-8

Cited by 9 publications

(2 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the 13 C NMR spectra, the signals at δ 80.1 and 170.5 correspond to the initial triazine and the signals at δ 164.6, 153.9, 106.5, and 80.4 correspond to tautomer 1а. Thus, based on results obtained, it is beleived that the equilibrium between triazine 1 and the dihydrotriazine 1a in a 15 : 85 ratio (Scheme 6) is estab lished in DMSO solution.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Thermodynamic stability of 2,4,6-tris(nitromethyl)-1,3,5-triazine: an experimental and theoretical study

et al. 2009

View full text Add to dashboard Cite

The molecular geometries and electronic structures of 2,4,6 tris(nitromethyl) 1,3,5 tri azine 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.Earlier, 1 we studied the possible reasons for stabiliza tion of 2,4,6 tris[di tert butoxycarbonyl methylidene] hexahydro 1,3,5 triazine in the hexahydrotriazine form. Despite the fact that the hexahydro 1,3,5 triazine struc ture could be less stable than the 1,3,5 triazine structure because of the loss of aromatiztion energy, this com pound exists only in the hexahydro 1,3,5 triazine form both in solution and in the solid phase. A possible reason for stabilization of hexahydro 1,3,5 triazine can be the presence of intramolecular hydrogen bonds. 1 Such bonds are also formed in acyclic 1 amino and 1,1 diamino ethylenes containing one or two acceptor groups, such as COOR, COR, CN, NO 2 at the C(2) atom. 2-6The existence of cyclic and acyclic derivatives of 1,1 diamino 2 nitroethylene, 1,1 diamino 2,2 dinitro ethylene, and 1 amino 2 nitroethylene mainly in the ethylene form stabilized by intramolecular hydrogen bond (Scheme 1) was discussed. 3,7,8 † Deseased. Scheme 1Z = H, R; X = H, R, NR 2 ; Y = H, R, acceptor group A relatively small number of papers 9-19 is devoted to the chemistry of nitromethyl derivatives (compounds con taining CH 2 NO 2 groups) of noncondensed six membered N heterocycles including 1,2,4 triazine. It is known 9 that nitromethylpyridines are in equilibrium with the nitronate form in DMSO solution (Scheme 2).For 4 (nitromethyl)pyridine, the amount of the nitronate form in solution does not exceed 30%. 12 Several examples of azinyl ylidene tautomeric equilibrium of noncon densed 13,14 and condensed 9,15-17 six membered N hetero cycles containing the nitromethyl gr...

show abstract

Section: Methodsmentioning

confidence: 99%

“…23 1 H and 13 C NMR spectra were recorded on Bruker AM 300 and Bruker DRX 500 instruments with Me 4 Si as an internal standard.…”

Section: Methodsmentioning

confidence: 99%