| Recently, high energy materials have received much attention. Because of the particularity of N-N bond (the average bond energy of N-N and N=N are 38.2 and 99.9 kcal/mol, respectively, 1/3 and 2/3 smaller than the N≡N bond), any reactions to release N2 should be accompanied with a large exothermicity. As the small unit azide N3, it has been studied both theoretically and experimentally. For the cyclic-N3, previous computational studies have suggested it as a precursor of the high energy material N4. However, in contrast to the linea-N3, it receives rather little attention. In this paper, we theoretically study the chemical stablily of cyclic-N3 whose details are as follows1) We study the mechanisms of cyclic-N3 with O2 and H2O at the level of G3B3//B3LYP/6-311++G(d, p). For cyclic-N3 reation with O2, we provide the potential energy surface (PES). From PES, the most feasible paths can be written as R cyclic-N3+O2→1→2→5→P1 N2+NO+3O, and R cyclic-N3+O2→1→3→2→5→P1 N2+NO+3O. They are both competitive. The resulted products are NO, 3O and N2, and they follow the mechanism of addition-elimition. For the whole reaction, the rate-determinating barrier is 12.8 (11.0) kcal/mol, so we consider that when cyclic-N3 coexists with oxygen at the room temperature, it is stable in kinetics. So when preparing cyclic-N3, isolating oxygen is not necessary; For the reaction system of cyclic-N3 + H2O, we also provide the potential enegy surface. Form PES, the dominant reaction path can be described as R cyclic-N3+H2O→1→2→P1 cyclic-N3H+OH, and it follows the H-abstraction mechanism. The rate-determinating barrier is 36.0 (36.2) kcal/mol which indicates that cyclic-N3 is inert toward H2O.2) We study the mechanisms of cyclic-N3 and NO, NO2, Cl2 at the level of G3B3//B3LYP/6-311+G(d). The reations of cyclic-N3 withπ-bond systems NO and NO2 prefer to react via the singlet PES following a mechanism of addition-elimination. The most fesible paths can be written as R cyclic-N3+NO→1NO-2→1NO-3→1NO-P2 (1cyclic-NON+N2) and R cyclic-N3+NO2→1NO2-1→1NO2-2→1NO2-P2 (1NNO(O)+ N2), respectively. For cyclic-N3 reation withσ-bond Cl2, the dominant path is R cyclic-N3+Cl2→1→2→Cl2-P1 (Cl+cyclic-N3Cl). The reaction follows a Cl-abstraction mechanism with the total barrier of 7.6(13.9) kcal/mol. In summary, the reaction can hardly happen. From the above analysis, we can predict that cyclic-N3 is active towards certain reactiveπ-bond molecules like NO and NO2. However, when it is towards theσ-bond moleure like Cl2, cyclic-N3 is inert.
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