Structural parameters of azines, calculated at the MP2(fc)/6-31G" and B3LYP/6-31G levels, were reported in a recent comprehensive theoretical study <2004CJC50>, with results for relevant azines shown in Figure 1. Both B3LYP and MP2 calculations showed that hexazine is a hilltop, whereas hexazine (Z>2) is a minimum, in [Pg.718]

The other two chapters deal with the application of molecular orbital theory to heterocyclic chemistry. The groups surveyed are (a) sulfur heterocycles and (6) azines. The chapters, which are authored by R. Zahradnik and J. Koutecky, discuss the relevance of theoretical calculation to reactivity, electronic structure, and other physicochemical properties of the compounds. The new techniques of theoretical chemistry have been applied with great success to carbocyclic compounds their significance in heterocyclic chemistry will surely increase. [Pg.412]

Therefore in the literature there are some N NMR data of ring fluorinated diazines. The N NMR of perfluorinated diazines are summarized in Table 7 [144], Also recently few works devoted to theoretical calculations of couphng constants in fluorinated azines were published [145,146], [Pg.325]

The tautomerism of functional derivatives of azines (e.g., pyridones) and other more complex systems (guanines, porphyrins, etc.) has been much studied both experimental and theoretically [40, 76-82], Our contribution to this field has been modest using a combination of 13C and 15N NMR in solution and in the solid state, together with GIAO//B3LYP/6-311++G calculations, the tautomerism of 2-pyri-done, 4(37/)-pyrimidone, uracil, and cytosine were determined [83], [Pg.164]

The parent azine systems discussed in this chapter, compounds 1-4, have not been prepared experimentally, but there has been continuing interest in their theoretical analysis. The past 10 years have seen the incorporation of computational chemistry into the mainstream of chemical research, facilitated by the advancement of computer hardware, and computational software and methods. Hence, not surprisingly, recent studies have been performed using advanced methods, such as MP2, CCSD, and a considerable number of density functional theory (DFT) calculations. Azines have been investigated in terms of structural features, aromaticity, kinetic and thermodynamic stability, and decomposition reactions. [Pg.718]

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