Nitrogen triiodide
| Nitrogen triiodide | |
|---|---|
| Nitrogen triiodide (structural formula) | |
| Molecular formula | NI3 |
| Molar mass | 394.77 g/mol |
| CAS number | [13444-85-4] |
| Density | ? g/cm3 |
| Solubility (water) | Decomposes |
| Melting point | Decomposes |
| Related halides | Nitrogen trifluoride Nitrogen trichloride Nitrogen tribromide |
| Related iodides | Phosphorus triiodide Arsenic triiodide |
| Disclaimer and references | |
Nitrogen triiodide, also called nitrogen iodide, is a highly explosive compound of nitrogen and iodine, NI3. It is a contact explosive, and small quantities explode with a gunpowder-like snap when touched by even a feather, releasing a volatile cloud of iodine vapor. The decomposition of nitrogen triiodide occurs via the following reaction:
- 2NI3 (s) → N2 (g) + 3I2 (g)
Pure nitrogen triiodide is a dark red compound, first prepared in 1990 by reaction of boron nitride with iodine fluoride in trichlorofluoromethane at -30°C.[1]
The compound usually referred to as nitrogen triiodide is an ammonia adduct, NI3·NH3, synthesized by reacting iodine with ammonia. It was first prepared by Bernard Courtois in 1812, and its formula was finally determined unequivocally in 1905 by Silberrad.[2] Its solid state structure consists of zig-zag chains of corner-sharing NI4 tetrahedra, with ammonia molecules between the chains.
Small amounts of nitrogen triiodide are sometimes synthesized as a demonstration to high school chemistry students. However, because the compound is so unstable, it has not been used in blasting caps or primers for explosives. While still wet, nitrogen triiodide is safer to handle than the dry compound, but is still prone to spontaneous explosion. NI3·NH3 explosions leave orange-to-purple iodine stains that are difficult to wash. However, they can be easily removed by sodium thiosulfate solution.
Nitrogen triiodide is so unstable because of the size difference between the two different types of atoms. The three iodine atoms are much bigger than the nitrogen atom holding them together. Because of this, not only is the bond between nuclei under much stress and therefore weaker, but the outside electrons of the different iodine atoms are very close, which increases the overall instability of the molecule.