Thermal decomposition pathways for 1,1-diamino-2,2-dinitroethene (FOX-7)

Area of Science:

• Computational chemistry
• Chemical kinetics
• Materials science

Background:

• 1,1-diamino-2,2-dinitroethene (FOX-7) is an energetic material.
• Understanding its thermal decomposition is crucial for safety and performance.
• Geminal dinitro compounds share structural similarities.

Purpose of the Study:

• To computationally investigate the gas-phase thermal decomposition mechanism of FOX-7.
• To identify the key exothermic steps and intermediates.
• To compare FOX-7's decomposition pathway with other geminal dinitro energetic materials.

Main Methods:

• Density Functional Theory (DFT) calculations.
• Transition State Theory (TST).
• Computational chemical kinetics modeling.

Main Results:

• Identified a novel 3-member cyclic intermediate mechanism for NO loss in radical intermediates.
• This pathway differs significantly from the typical nitro-nitrite isomerization.
• Determined the primary exothermic step governing FOX-7 decomposition.

Conclusions:

• The decomposition of FOX-7 proceeds via a unique pathway involving a cyclic intermediate.
• This finding provides new insights into the stability and reactivity of FOX-7.
• The study highlights differences in decomposition mechanisms among geminal dinitro energetic materials.