Influence of N‑Oxide Introduction on the Stability of Nitrogen-Rich Heteroaromatic Rings: A Quantum Chemical Study

N-Oxidization is an important strategy for enhancing the density and energy of energetic materials. Nevertheless, the influence of N⁺–O^– introduction on molecular stability remains relatively unknown. Thus, the present work comprehensively studied 102 basic N-rich ring structures, including azoles, furazans, and azines, as well as their N-oxides by quantum chemical calculations. The introduction of N⁺–O^– weakens molecular stability in most cases because the process elongates chemical bonds, decreases ring aromaticity, narrows the gaps between the highest occupied and lowest unoccupied molecular orbitals, and increases the photochemical reactivity. Besides, the easy H transfer to the neighboring O atom, which forms a N–OH isomer in azoles, renders the stabilization by N-oxide introduction ineffective. However, N-oxide introduction can enhance the molecular stability of 1,2,3,4-tetrazine-1,3-dioxide and tetrazino-tetrazine 1,3,6,8-tetraoxide by promoting σ–π separation and relieving lone-pair repulsion. Moreover, the alternate arrangement of positive and negative charges is another factor stabilizing the 1,2,3,4-tetrazine ring by 1,3-dioxidation. Finally, we assess the accessibility of N-oxidized azoles and azines by regarding N₂O and H₂O₂ as oxidizers. We find that all the oxidations were exothermic, thermodynamically spontaneous, and kinetically feasible. After an overall evaluation, we propose 19 N-oxides as basic structures for high-energy materials with considerable stability

GA parameters settings.

<p>GA parameters settings.</p

Model validation of the LQR-GA controller.

<p>(a) Comparison of experimental data and simulated results at 30 knots & SSN4. (b) Comparison of experimental data and simulated results at 40 knots & SSN4. (c) Comparison of experimental data and simulated results at 40 knots & SSN5. (d) Comparison of experimental data and simulated results at 40 knots & SSN6. (e) Comparison of experimental data and simulated results at 50 knots & SSN4.</p

A WPC with a T-foil and two flaps.

<p>A WPC with a T-foil and two flaps.</p

SIMULINK diagrams of the controlled WPC.

<p>SIMULINK diagrams of the controlled WPC.</p

The weighting parameters and the desired gain in different SSN and speeds.

<p>The weighting parameters and the desired gain in different SSN and speeds.</p

A 2 DoF WPC rigid body moving in a three-dimensional space.

<p>A 2 DoF WPC rigid body moving in a three-dimensional space.</p

Effects of WPC ride control with LQR-GA approach on heave and pitch.

<p>(a) Heave. (b) Pitch.</p

Nominal physical parameters of WPC.

<p>Nominal physical parameters of WPC.</p

An interactive screen of GA SIMULINK diagram.

<p>An interactive screen of GA SIMULINK diagram.</p