Nitrogen triiodide

Nitrogen triiodide is an inorganic compound with the formula NI3. It is an extremely sensitive contact explosive: small quantities explode with a loud, sharp snap when touched even lightly, releasing a purple cloud of iodine vapor; it can even be detonated by alpha radiation. NI3 has a complex structural chemistry that is difficult to study because of the instability of the derivatives.

Nitrogen triiodide
Nitrogen triiodide
Nitrogen triiodide
Names
IUPAC name
Triiodoamine
Other names
Nitrogen iodide
Ammonia triiodide
Triiodine nitride
Triiodine mononitride
Triiodamine
Identifiers
3D model (JSmol)
ChemSpider
Properties
NI3
Molar mass 394.719 g/mol
Appearance purple gas
Boiling point sublimes at −20 °C
Insoluble
Solubility organic solvents,[1] such as diethyl ether
Hazards
Main hazards Extremely explosive
NFPA 704 (fire diamond)
Flammability code 0: Will not burn. E.g. waterHealth code 0: Exposure under fire conditions would offer no hazard beyond that of ordinary combustible material. E.g. sodium chlorideReactivity code 4: Readily capable of detonation or explosive decomposition at normal temperatures and pressures. E.g. nitroglycerinSpecial hazards (white): no code
0
0
4
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Structure of NI3 and its derivatives

Nitrogen triiodide was first characterized by Raman spectroscopy in 1990 when it was prepared by an ammonia-free route. Boron nitride reacts with iodine monofluoride in trichlorofluoromethane at −30 °C to produce pure NI3 in low yield:[2]

BN + 3 IF → NI3 + BF3

NI3 is pyramidal (C3v molecular symmetry), as are the other nitrogen trihalides and ammonia.[3]

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 Oswald Silberrad.[4] 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 NI3 · NH3 can be attributed to the large steric strain caused by the three large iodine atoms being held in proximity to each other around the relatively tiny nitrogen atom. This results in a very low activation energy for its decomposition, a reaction made even more favorable due 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 greatly 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 in the form of 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:[3]

8 NI3 · NH3 → 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".[5] To highlight the sensitivity of the compound, it is usually detonated by touching it with a feather but even the slightest air current, laser light, 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.[6]

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References
  1. 4. Analytical techniques. acornusers.org
  2. Tornieporth-Oetting, I.; Klapötke, T. (1990). "Nitrogen Triiodide". Angewandte Chemie International Edition. 29 (6): 677–679. doi:10.1002/anie.199006771.
  3. Holleman, A. F.; Wiberg, E. (2001). Inorganic Chemistry. San Diego: Academic Press. ISBN 0-12-352651-5.
  4. Silberrad, O. (1905). "The Constitution of Nitrogen Triiodide". Journal of the Chemical Society, Transactions. 87: 55–66. doi:10.1039/CT9058700055.
  5. Ford, L. A.; Grundmeier, E. W. (1993). Chemical Magic. Dover. p. 76. ISBN 0-486-67628-5.
  6. Bowden, F. P. (1958). "Initiation of Explosion by Neutrons, α-Particles, and Fission Products". Proceedings of the Royal Society of London A. 246 (1245): 216–219. doi:10.1098/rspa.1958.0123.
Salts and covalent derivatives of the nitride ion
NH3
N2H4		 He(N2)11
Li3N Be3N2 BN β-C3N4
g-C3N4
CxNy		 N2 NxOy NF3 Ne
Na3N Mg3N2 AlN Si3N4 PN
P3N5		 SxNy
SN
S4N4		 NCl3 Ar
K3N Ca3N2 ScN TiN VN CrN
Cr2N		 MnxNy FexNy CoN Ni3N CuN Zn3N2 GaN Ge3N4 As Se NBr3 Kr
Rb3N Sr3N2 YN ZrN NbN β-Mo2N Tc Ru Rh PdN Ag3N CdN InN Sn Sb Te NI3 Xe
Cs3N Ba3N2   Hf3N4 TaN WN Re Os Ir Pt Au Hg3N2 TlN Pb BiN Po At Rn
Fr3N Ra3N2   Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og
↓
La CeN Pr Nd Pm Sm Eu GdN Tb Dy Ho Er Tm Yb Lu
Ac Th Pa UN Np Pu Am Cm Bk Cf Es Fm Md No Lr
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