Theoretical investigation of the synthesis mechanism of dinitraminic acid (HDN) through ammonium amidosulfonate nitration in H2SO4/HNO3 mixed solvent

Density functional theory (DFT) was employed to systematically investigate the stepwise nitration mechanism of ammonium amidosulfonate (NH₄SO₃NH₂) with the NO₂⁺ ion in a mixed H₂SO₄/HNO₃ solvent environment in synthesising dinitraminic acid (HDN). Within the temperature range from 253.15 to 293.15 K at 0.1 MPa, the thermodynamic and kinetic parameters along the reaction pathway were obtained. The results reveals that the reaction follows a two-step electrophilic nitration mechanism, that is, the reaction initiates with the formation of a complex between NH₄SO₃NH₂ and NO₂⁺ (or NO₂HSO₄), which then undergoes the first nitration event via a rate-determining transition state to generate the key intermediate H₂N–NO₂. Subsequently, this intermediate reacts with NO₂HSO₄ through a second transition state to yield the final product HDN. As the temperature increases from 253.15 to 293.15 K at 0.1 MPa, the thermodynamic and kinetic profiles of the reactions are altered. This work elaborates how temperature regulates the reaction pathway in a complex solvated system, thereby establishing a theoretical foundation for the efficient and controllable synthesis of HDN. And it will provide valuable insights into the actual nitration process and promote the practical application of HDN-based energetic materials.