AbstractThe reactivity of sodium azide, activated sodium azide and hydrazinium azide towards various dioxygenyl salts was studied. Under no circumstances the formation of dioxygenyl azide, O2N3, could be observed. This is in agreement with high level quantumchemical ab initio computations at correlated level (MP2, PMP2, CISD), predicting the decomposition of hypothetical O2+(g)/N3−(g) to be thermodynamically highly favorable (MP2: −326; PMP2: −328; CISD; −369 [kcal/mol]). The combustion of O2BF4with either N2H5N3(spontaneous reaction on contact in a coaxial solid‐propellant system) or NaN3(safe to handle, highly exothermic reaction after ignition) is discussed in terms of high‐energy‐density materials (HEDM).\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l} {\rm NaN}_{\rm 3} + {\rm O}_{\rm 2} {\rm BF}_{\rm 4} + 4/3\,{\rm Al} \rightarrow {\rm NaBF}_{\rm 4} + 3/2\,{\rm N}_{\rm 2} + 2/3\,{\rm Al}_{\rm 2} {\rm O}_{\rm 3} \\ \Delta {\rm H = - 434}\,{\rm kcal/mol} \\ \end{array} $$