Figure 1. Gibbs free-energy profile for the substitution reaction of the
amino group of FOX-7 by CH3NHNH2
In Figure 2, the subsequent reaction of the intermediate IM2 is carried
out according to the reaction path proposed by Xu [20]. The H on the
-NHNHCH3 group of IM2 is transferred to another C on the
alkenyl group, via the transition state TS3 with an energy barrier of
44.3 kcal/mol, forming the intermediate IM3. Subsequently, the H on the
C of the alkenyl group of the intermediate IM3 is transferred to the O
of the nitro group to form the intermediate IM4, in which the energy
barrier of the transition state TS4 is higher, and this step is
difficult to carry out. The H on the N of the -NNHCH3group of IM4 is approached to the O on the nitro group through the
rotation of the dihedral angle to form IM5, which is conducive to the
next H transfer reaction. The H on the N of the -NNHCH3group of IM5 is transferred to the O on the nitro group, forming the
intermediate IM6 with two H atoms in the nitro group. Subsequently, the
N atom on the nitro group is approached by the N atom on
-NNCH3 group, forming IM7 with a triazole ring
structure. IM7 is unstable, and the -OH group on the N of the triazole
ring is immediately combined by H to decompose into a
H2O molecule and stable IM8 intermediates. The
NH3 generated earlier in this reaction is combined with
IM8 to form the product MNTzA. According to the reaction energy barrier,
it can be seen that the TS4 is higher in the reaction path of the
transfer of H on the alkenyl group of IM3 to O on the nitro group, so
the reaction path proposed by Xu is carried out difficultly.