Figure 2. Gibbs free-energy profile for the production of MNTzA according scheme 2.
In Figure 3, the cyclization reaction of the triazole ring is performed first. Through the rotation of the dihedral angle, the N on the -NHNHCH3 group is approached to the N on the nitro group, forming an intermediate IM3’, which facilitates the subsequent formation of a triazole ring structure. The triazole ring is formed by the formation of a bond between the N on the -NHNHCH3group of IM3’ and the N on the nitro group, and the H on the -NHNHCH3 group is transferred synergistically to the O on the nitro group, forming intermediate IM4’. The H on the triazole ring of IM4’ is transferred to the -OH group to generate the H2O molecule and the intermediate IM8. Finally, the NH3generated earlier in this reaction is combined with IM8 to form the product MNTzA. Comparing the reaction mechanisms of Figure 2 and Figure 3, it can be found that the energy barrier of the rate-determining step TS4’ is lower than that of TS4, and the reaction pathway of Figure 2 is more likely to proceed.