Quantum-chemical modeling of the mechanism for formation of HNO3 from NO2 and water

ReaxFF-Based Molecular Dynamics Study of the Mechanism of the Reaction of N2O4 with H2O

During long-term storage of the liquid propellant N2O4, it absorbs H2O to form the N2O4(H2O)n system, and this in turn generates HNO3, HNO2, and other substances in the storage tank because of corrosion, which seriously affects the performance of weaponry. In this work, we carried out computational simulations of N2O4 with different masses of water based on ReaxFF, analyzed the reaction intermediates and products, and investigated the mechanism of the reaction of N2O4 with H2O and of N2O4(H2O)n. The results show that the reaction product ω(HNO3+HNO2) undergoes a rapid growth in the early stage of the reaction and then tends toward dynamic equilibrium; the potential energy of the system decreases with the increase of ω(H2O), the reaction rate increases, and the rate of decomposition of HNO2 to form HNO3 increases. When ω(H2O) is 0.2 or 1.0%, the intermediate products are N2O4H2O or N2O4(H2O)2, respectively, and the reaction proceeds along two paths; when ω(H2O) ≥ 2.0%, N2O4(H2O)3 appears as the intermediate product, HNO3 and HNO2 are directly produced in one step, and a stable current loop can be formed within the whole system.

Isomerization and reaction process of N2O4(H2O) n

Liquid propellant N2O4 is prone to absorb H2O to form an N2O4(H2O) n system during long-term storage, ultimately generating HNO3, HNO2, and other substances capable of corroding the storage tank, which will adversely affect the performance of weapons and equipment. In this work, the reaction process of the N2O4(H2O) n system is simulated using density functional theory, and the potential energy surface, the geometric configurations of the molecules, the charge distribution, and the bond parameters of the reaction course at n = 0-3 are analyzed. The results show that the potential energy of the system is lower and the structure is more stable when the H2O in the N2O4(H2O) n system is distributed on the same side. When n = 1 or 2, the reaction profiles are similar, and the systems are partly ionic, although still mainly covalently bonded. When n = 3, the charge on the trans-ONONO2 group and the ON-ONO2 bond length change abruptly to -0.503 a.u. and 2.57 Å, respectively, at which point the system is dominated by ionic bonds. At n = 2, a proton-transfer phenomenon occurs in the reaction course, with partial reverse charge-transfer from NO3 - to NO+, making the ON-ONO2 bond less susceptible to cleavage, further verifying that N2O4(H2O) n tends to afford the products directly in one step as H2O accumulates in the system.

Development of Nitrolactonization Mediated by Iron(III) Nitrate Nonahydrate

The nitrolactonization of alkenyl carboxylic acids mediated by Fe(NO₃)₃·9H₂O has been developed. Nitrolactones were obtained in up to 93% yield by treatment of alkenyl carboxylic acids with Fe(NO₃)₃·9H₂O. Mechanistic studies disclosed that the reaction proceeded through a radical intermediate generated from addition of NO₂ to alkenyl carboxylic acids.

Mechanism for formation of atmospheric Cl atom precursors in the reaction of dinitrogen oxides with HCl/Cl− on aqueous films

Formation of atmospheric chlorine atom precursors ClNO₂ and ClNO in the reaction of HCl with oxides of nitrogen on a water film: left – formation of N–Cl bond as N–O bond breaks; right – concurrent changes in Mulliken charges.