科研之友
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摘要
The reaction mechanism, thermodynamic and kinetic properties for diazotization and nitration of 3,5-diamino-1,2,4-triazole were studied by a density functional theory. The geometries of the reactants, transition states, and intermediates were optimized at the B3LYP/6-31G (d, p) level. Vibrational analysis was carried out to confirm the transition state structures, and the intrinsic reaction coordinate (IRC) method was used to explore the minimum energy path. The single-point energies of all stagnation points were further calculated at the B3LYP (MP2)/6-311+G (2d, p) level. The statistical thermodynamic method and Eyring transition state theory with Wigner correction were used to study the thermodynamic and kinetic characters of all reactions within 0-25 degrees C. Two reaction channels are computed, including the diazotization and nitration of 3-NH(2) or 5-NH(2), and there are six steps in each channel. The reaction rate in each step is increased with temperature. The last step in each channel is the slowest step. The first, second, and fifth steps are exothermic reactions, and are favored at lower temperature in the thermodynamics.
