Nitrogen triiodide is an

inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemis ...

with the formula N I₃. 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 Iodine is a chemical element with the Symbol (chemistry), symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a semi-lustrous, non-metallic solid at standard conditions that melts to form a deep violet liquid at , ...

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. Although nitrogen is more

electronegative Electronegativity, symbolized as , is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. An atom's electronegativity is affected by both its atomic number and the ...

than iodine, the compound was so named due to its analogy to the compound nitrogen trichloride.

Structure of NI₃ and its derivatives

Nitrogen triiodide was first characterized by

Raman spectroscopy Raman spectroscopy () (named after Indian physicist C. V. Raman) is a spectroscopic technique typically used to determine vibrational modes of molecules, although rotational and other low-frequency modes of systems may also be observed. Raman ...

in 1990 when it was prepared by an ammonia-free route. Boron nitride reacts with

iodine monofluoride Iodine monofluoride is an interhalogen compound of iodine and fluorine with formula IF. It is a chocolate-brown solid that decomposes at 0 °C, disproportionating to elemental iodine and iodine pentafluoride: :5 IF → 2 I2 + IF5 However, ...

in trichlorofluoromethane at −30 °C to produce pure NI₃ in low yield: :BN + 3 IF → NI₃ + BF₃ NI₃ is pyramidal (C_3v

molecular symmetry Molecular symmetry in chemistry describes the symmetry present in molecules and the classification of these molecules according to their symmetry. Molecular symmetry is a fundamental concept in chemistry, as it can be used to predict or explain m ...

), as are the other nitrogen trihalides and

ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous ...

. The material that is usually called "nitrogen triiodide" is prepared by the reaction of iodine with

. 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 Oswald J. Silberrad (1878 – 17 June 1960) was a British chemist who specialised in explosives, the related field of dye stuffs, and metallurgy. Life and works Silberrad was born at Buckhurst Hill in Essex and was the younger brother of th ...

. 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. NH3·NI3-chain-from-xtal-3D-bs-20

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 In chemistry and physics, activation energy is the minimum amount of energy that must be provided for compounds to result in a chemical reaction. The activation energy (''E''a) of a reaction is measured in joules per mole (J/mol), kilojoules p ...

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 Nitroglycerin (NG), (alternative spelling of nitroglycerine) also known as trinitroglycerin (TNG), nitro, glyceryl trinitrate (GTN), or 1,2,3-trinitroxypropane, is a dense, colorless, oily, explosive liquid most commonly produced by nitrating g ...

is powerful and also greatly shock-sensitive (although not nearly as much so as nitrogen triiodide, which can be set off with the touch of a feather), it was only due to

phlegmatizers A phlegmatizer is a compound that minimizes the explosive tendency of compound or material. The term is derived from the word phlegmatic, meaning 'not easily excited'. Many chemical compounds that are potentially explosive have useful non-explosiv ...

that nitroglycerin's shock sensitivity was reduced and it became safer to handle and transport in the form of

dynamite Dynamite is an explosive made of nitroglycerin, sorbents (such as powdered shells or clay), and stabilizers. It was invented by the Swedish chemist and engineer Alfred Nobel in Geesthacht, Northern Germany, and patented in 1867. It rapidl ...

. 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: : 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 Sodium thiosulfate (sodium thiosulphate) is an inorganic compound with the formula . Typically it is available as the white or colorless pentahydrate, . The solid is an efflorescent (loses water readily) crystalline substance that dissolves well ...

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." 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 Alpha particles, also called alpha rays or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. They are generally produced in the process of alpha decay, but may also be prod ...

and

nuclear fission Nuclear fission is a reaction in which the nucleus of an atom splits into two or more smaller nuclei. The fission process often produces gamma photons, and releases a very large amount of energy even by the energetic standards of radio ...

products.

References

External links

See the explosion
* ttps://www.youtube.com/watch?v=2KlAf936E90 Nitrogen Tri-Iodide Detonation on Youtube {{Nitrides Inorganic amines Iodides Nitrogen halides Explosive chemicals Pyrotechnic chemicals

Structure of NI3 and its derivatives

Decomposition and explosiveness

References

External links

Structure of NI₃ and its derivatives