Azidotetrazolate (CN7−) is an anion which forms a highly explosive series of salts. The ion is made by removing a proton from 5-azido-1H-tetrazole. The molecular structure contains a five-membered ring with four nitrogen atoms, and an azido side chain connected to the carbon atom. Several salts exist, but they are unstable and spontaneously explode.[1] For example, the rubidium, potassium and caesium salts are so unstable that they explode while crystallizing.[1]
Azidotetrazolates are under investigation for use as bullet propellant, rocket propellants and high explosives. The nitrogen base compounds have the advantage of being "green explosives", meaning that their waste products are safe.[1] Amongst the tetrazolates, they have the highest nitrogen fraction.[2]
Properties
editDifferent stimuli can set off explosions. Possibilities include impact, friction, sparks or heat. Guanidinium azidotetrazolate could be melted to an ionic liquid at 100°C, but would decompose smoothly at 159°. Sodium azidotetrazolate explodes when the temperature reaches 155°C.[1]
The CNNNN ring in azidotetrazolate is planar and aromatic. The NNN side chain is attached to the carbon atom, and bent at the first nitrogen so that it is roughly parallel to the ring.[3]
The base acids, 5-azido-1H-tetrazole and 5-azido-2H-tetrazole both can exist. The 1H version has a hydrogen atom bonded to a nitrogen atom next to the carbon. It is the stable form in solids and solutions in polar liquids. This is explained by a favourable hydrogen bond, and a greater dipole moment. The 2H version with hydrogen attached in the second nitrogen from the carbon is purportedly more stable in the gas phase.[4]
Formation
editThe azidotetrazolate ion can be made from cyanogen bromide and sodium azide in water:[1]
BrCN + 2NaN3 → N4CN3− + Na+ + NaBr
Salts
edit| formula[1] | name | molecular weight | density | structure | unit cell dimension Å | cell volume | formula per cell | Specific impulse | melt °C | decompose °C | CAS[5] |
|---|---|---|---|---|---|---|---|---|---|---|---|
| NH4CN7 | Ammonium azidotetrazolate | 128.12 | 1.608 | monoclinic | a=3.9103 b=6.9140 c=9.9127 β=99.177° | 264.57 | 2 | 248 | 157 | 35038-47-2 | |
| N2H5CN7 | Hydrazinium azidotetrazolate | 143.14 | 1.568 | monoclinic | a=10.8114 b=7.4641 c=7.6676 β=101.437° | 606.47 | 4 | 265 | 136 | ||
| CN3H6CN7 | guanidinium azidotetrazolate semihydrate | 358.35 | 1.546 | monoclinic | a=9.5374 b=15.3120 c=10.5731 β=94.361 | 1539.6 | 4 | 100 | 159 | ||
| CN4H7CN7 | aminoguanidinium azidotetrazolate | 185.19 | 1.524 | triclinic | a=9.7652 b=9.7803 c=10.0434 α=71.327° β=74.399° γ=63.962° | 807.2 | 4 | 228 | |||
| NH3OHCN7 | Hydroxylammonium azidotetrazolate[6] | 144.12 | 1.649 | monoclinic | a=3.677 b=20.885 c=7.641 β=98.367 | 580.5 | 4 | ||||
| LiCN7•H2O | Lithium azidotetrazolate monohydrate | 135.03 | 1.683 | monoclinic | a=8.9207 b=4.6663 c=12.8648 β=95.608 | 532.96 | 4 | ||||
| NaCN7•H2O | sodium azidotetrazolate monohydrate | 151.09 | 1.743 | monoclinic | a=11.203 b=7.138 c=14.409 β=91.630° | 1151.8 | 8 | explode | 155 | 35038-45-0 | |
| KCN7 | Potassium azidotetrazolate | 149.18 | 1.917 | monoclinic | a=9.7759 b=6.2990 c=8.4533 β=96.720° | 516.96 | 4 | ||||
| RbCN7 | Rubidium azidotetrazolate | 195.12 | Unknown; all attempts at isolation terminated by detonation of solution. | <25 | |||||||
| CsCN7 | Caesium azidotetrazolate | 242.99 | 2.810 | orthorhombic | a=4.3082 b=7.1345 c=18.6869 | 574.38 | 4 | ||||
| 3Ca(CN7)2•16H2O | Calcium azidotetrazolate | 1068.98 | 1.657 | monoclinic | a=24.448 b=6.616 c=28.057 β=109.246° | 4285 | 4 | ||||
| AgCN7 | silver azidotetrazolate | ||||||||||
| HCN7 | 5-Azido-1H-tetrazole | 111.07 | 1.72 | 75 | 165 | 35038-46-1 | |||||
Related
editChemicals related to the azidotetrazolate anion include 1-diazidocarbamoyl-5-azidotetrazole with the same percentage of nitrogen.
References
edit- ^ a b c d e f Klapötke, Thomas M.; Stierstorfer, Jörg (28 January 2009). "The CN7- Anion". Journal of the American Chemical Society. 131 (3): 1122–1134. doi:10.1021/ja8077522. PMID 19115947.
- ^ Petkewich, Rachel A. "High-Nitrogen Anion Exceeds The Power Of RDX | January 12, 2009 Issue - Vol. 87 Issue 2 | Chemical & Engineering News". cen.acs.org.
- ^ Zhaoxu, Chen; Jianfen, Fan; Heming, Xiao (January 1999). "Theoretical study on tetrazole and its derivatives. Part 7: ab initio MO and thermodynamic calculations on azido derivatives of tetrazole". Journal of Molecular Structure: THEOCHEM. 458 (3): 249–256. doi:10.1016/S0166-1280(98)00249-8.
- ^ Stierstorfer, Jörg; Klapötke, Thomas M.; Hammerl, Anton; Chapman, Robert D. (June 2008). "5-Azido-1H-tetrazole – Improved Synthesis, Crystal Structure and Sensitivity Data". Zeitschrift für anorganische und allgemeine Chemie. 634 (6–7): 1051–1057. doi:10.1002/zaac.200800003.
- ^ Marsh, F. D. (September 1972). "Cyanogen azide". The Journal of Organic Chemistry. 37 (19): 2966–2969. doi:10.1021/jo00984a012.
- ^ Klapötke, Thomas M.; Piercey, Davin G.; Stierstorfer, Jörg (11 November 2011). "The Taming of CN7−: The Azidotetrazolate 2-Oxide Anion". Chemistry - A European Journal. 17 (46): 13068–13077. doi:10.1002/chem.201102064. PMID 21971954.
External links
edit- Derek, Lowe (7 January 2009). "Things I Won't Work With: Azidotetrazolate Salts". In the Pipeline. Retrieved 11 February 2018.