Pyridylpentazole and its derivatives: a new source of N5−?

Abstract

Pyridylpentazole (PyN₅) and its derivatives with 1–2 electron withdrawing groups (–NO₂, –CN, –CF₃ and –NF₂) were studied using density functional theory to assess their potentials as the source of pentazole anion N₅⁻ for replacement of phenylpentazole (PhN₅). N₅⁻ can be produced more easily from PyN₅s because the activation energies (E_a,1 = 364.7–387.1 kJ mol⁻¹) for the cleavage of the central C–N bonds of PyN₅s are lower than that of PhN₅ (395.3 kJ mol⁻¹) and the C–N bond decomposition reactions of the former are faster than that of the latter. The energies (E_a,2) required for dissociation of the N₅ ring of PyN₅s (67.6–84.1 kJ mol⁻¹) are smaller than that of PhN₅ (88.7 kJ mol⁻¹), and the rates of the former are faster than that of the latter. Comparing the stabilities of the C–N bond and the N₅ ring of PyN₅s and PhN₅, the decrement in the C–N bond stability (2.1–7.8%) caused by the pyridine ring and substituents is less obvious than that of the N₅ ring (12.7–23.7%). Although N₅⁻ can be obtained more easily and faster from PyN₅s than PhN₅, the smaller E_a,2 makes PyN₅s less stable than PhN₅, so pyridylpentazoles may not be a better source of N₅⁻ than phenylpentazole.