- Nitrogen triiodide
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Nitrogen triiodide 
triiodoamineOther namesnitrogen iodide, triiodine nitrideIdentifiers CAS number 13444-85-4 
PubChem 61603 ChemSpider 55511 Jmol-3D images Image 1 - IN(I)I
- InChI=1S/I3N/c1-4(2)3
Key: FZIONDGWZAKCEX-UHFFFAOYSA-N
Properties Molecular formula NI3 Molar mass 394.719 g/mol Appearance red solid Solubility in water no 
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)Infobox references Nitrogen triiodide is the inorganic compound with the formula NI3. It is an extremely sensitive contact explosive: small quantities explode with a gunpowder-like snap when touched even lightly, releasing a purple cloud of iodine vapor. NI3 has a complex structural chemistry that is difficult to study because of the instability of the derivatives.
Contents
Structure of NI3 and its derivatives
Nitrogen triiodide was first characterized by X-ray crystallography in 1990 when it was prepared by an ammonia-free route. Boron nitride reacts with iodine fluoride in trichlorofluoromethane at −30 °C to produce pure NI3 in low yield:[1]
- BN + 3IF → NI3 + BF3
NI3 is pyramidal (C3v molecular symmetry), as are the other nitrogen trihalides as well as ammonia.[2]
The material that is usually called "nitrogen triiodide" is prepared by the reaction of iodine with ammonia. When this reaction is conducted at low temperatures in anhydrous ammonia, the initial product is NI3·(NH3)5, but this material loses some ammonia upon warming to give the 1:1 adduct NI3·(NH3). This adduct was first reported by Bernard Courtois in 1812, and its formula was finally determined in 1905 by Silberrad.[3] Its solid state structure consists of chains of -NI2-I-NI2-I-NI2-I-... Ammonia molecules are situated between the chains. When kept cold in the dark and damp with ammonia, NI3·(NH3) is stable.
Decomposition and explosiveness
The instability of NI3 and NI3NH3 can be attributed to the great stability of N2. Nitrogen triiodide has no practical commercial value due to its extreme shock sensitivity, making it impossible to store, transport, and utilize for controlled explosions. Whereas pure nitroglycerin is also highly shock-sensitive (although not nearly as much so as nitrogen triiodide, which can be set off with the touch of a feather) and powerful, it was only due to phlegmatizers that its shock sensitivity was reduced and it became safer to handle and transport as dynamite.
The decomposition of NI3 proceeds as follows to give nitrogen gas and iodine:
- 2 NI3 (s) → N2 (g) + 3 I2 (g) (–290 kJ/mol)
However, the dry material is a contact explosive, decomposing approximately as follows:[2]
- 8 NI3NH3 → 5 N2 + 6 NH4I + 9 I2
Consistent with this equation, these explosions leave orange-to-purple stains of iodine, which can be removed with sodium thiosulfate solution. An alternate method of stain removal is to simply allow the iodine time to sublime. Small amounts of nitrogen triiodide are sometimes synthesized as a demonstration to high school chemistry students or as an act of "chemical magic".[4] To highlight the sensitivity of the compound, it is usually detonated by touching it with a feather but even the slightest air current or other movement can cause detonation. Nitrogen triiodide is also notable for being the only known chemical explosive that detonates when exposed to alpha particles and nuclear fission products.[5]
References
- ^ Tornieporth-Oetting, I.; Klapötke, T. (1990). "Nitrogen Triiodide". Angewandte Chemie International Edition 29: 677–679. doi:10.1002/anie.199006771.
- ^ a b Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
- ^ Silberrad, O. "On the Constitution of Nitrogen Triiodide" Journal of the Chemistry Society 1905, volume 87, pages 55-66. doi:10.1039/CT9058700055
- ^ Ford, L. A. and Grundmeier, E. W. Chemical Magic. Dover, 1993, p. 76. ISBN 0486676285
- ^ Bowden, F. P. Initiation of explosion by neutrons, α-particles, and fission products. Proc. Roy. Soc. (London) 1958, A246, 216-19.
External links
Categories:- Inorganic amines
- Iodides
- Nitrogen halides
- Explosive chemicals
- Pyrotechnic chemicals
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