Tetrazole azide

Whitehead et al. carried out novel calculations on the tetrazole-azide equilibrium 1-7, (Scheme 2) and found that PM3 provided the best results <2001JMT199>. The computed heats of formation showed that the equilibrium is shifted to the ring-closed form in the case of electron-donating substituents in meta position to the pyridine nitrogen atom. 

Many tetrazoles are low brisance expls, and those containing tetrazole rings linked to chains of nitrogen atoms, such as Tetrazole Azide (see below) or 1,6-Ditetrazolylhexadiene (Vol 7, H91-L R) are exceedingly sensitive to heat and impact. Probably Diazotetrazole (Vol 5, D1176-L) represents the extreme in expl properties because it explds even in dilute aq solns (as low as 2%) and at temps as low as 0U. The expl derivatives of tetrazole are presented below ... 

IR spectroscopy was successfully exploited in studies of ring-chain tetrazole-azide isomerism of some fused tetrazoles. The presence or absence of a peak near 2100cm-1 corresponding to vibrations of an azide group, and also bands of the tetrazole ring in solid state and solutions, may be utilized for estimation of the dominant isomer and its relative amount <1999JST(510)165, 2006JOC4049>. 

Although the tetrazole-azide equilibrium was the subject of numerous earlier investigations <84CHEC-i(5)860> some novel results have also been published. Interest especially focussed on those cases where the ring closure of the a-azidoazine can occur in two directions (i.e. a ternary azide-tetrazole equilibrium can be formed). (See also sections 8.18.6.1. and 8.18.6.2.)... 

An NMR study has shown that the amino form (419) is the predominant tautomer of 2-[arylamino(imino)]-4a,5,6,7,8,8a-hexahydro-(47f)-l,3,4-benzoxadiazines. The proton-transfer tautomerism of 4-azabenzimidazole, mediated by hydrogen-bonded complexes, has been studied in the ground and excited states by means of absorption and emission spectroscopy, and it has been shown that 6-nitro and 8-nitro groups in the tetrazolo[l,5-a]pyridine molecule exhibit completely different influences on the tetrazole-azide equilibrium. The solvent effect on the azo-hydrazone tautomeric equilibrium of l-phenylazo-4-naphthol has been modelled by using ab initio quantum-chemical calculations. The results have shown that the hydrazone form is more stable in water, while methanol stabilizes the azo form. ... 

Another way of preparing 5-azidotetrazole is based on the diazotization reaction. 5-ATZ is mostly used as the starting material. Tetrazole diazonium salt forms as an intermediate which is converted into the desired tetrazole azide by treatment with sodium azide [84]. 

Hammerl, A., Klapotke, T.M., Noth, H., Warchhold, M. Synthesis, structure, molecular orbital and valence bond calculations for tetrazole azide, CHN7. Propellants Explosives Pyrotechnics 28, 165-173 (2003)... 

The position of the tetrazole-azide tautomerism in CDClj solution can be simply assigned by employing [3(C-8a)(ppm)] and N chemical shifts S (ppm) (Scheme 5.8) [24]. 

A comprehensive analysis of the tetrazole-azide ring-chain tautomerism of azoles has been published recently by Alkorta et al. [26]. 

---