Erythritol tetranitrate

History

ETN was discovered by John Stenhouse in 1849 by nitrating erythritol he recently discovered. He described its explosive properties but suggested an incorrect formula due to atomic weights not yet being accurately determined.

Its vasodilator properties have been researched since 1895.

DuPont researched the explosive after the war, getting a patent in 1928, but it was never commercialized due to the difficulty of erythritol synthesis. Only due to genetically-engineered yeasts in the 1990s did it become possible for the carbohydrate to become widely available.

Properties

ETN has a relatively high velocity of detonation of 8206 m/s at a density of ). It is white in color and odorless. ETN is commonly cast into mixtures with other high explosives. ETN dissolves readily in acetone and other ketone solvents. The impact and friction sensitivity is slightly higher than the sensitivity of pentaerythritol tetranitrate (PETN). The sensitivity of melt cast and pressed ETN is comparable. Lower nitrates of erythritol, such as erythritol trinitrate, are soluble in water, so they do not contaminate most ETN samples.

Much like PETN, ETN is known for having a very long shelf life. Studies that directly observed the crystalline structure saw no signs of decomposition after four years of storage at room temperature. ETN has a melting point of 61 C, compared to PETN which has a melting point of 141.3 C. Recent studies of ETN decomposition suggested a unimolecular rate-limiting step in which the bond is cleaved and begins the decomposition sequence.

Even small samples of ETN on the order of can cause relatively powerful explosions verging on detonation when heated without confinement, e.g. when placed on a layer of aluminium foil and heated with flame from below.

ETN can be melt-cast in warm (about 65 C) water. Slight decomposition is possible (often displayed by change in color from white to very light yellow). No reports of runaway reactions leading to explosion have been confirmed. However, the handling sensitivity in molten state is extremely poor (e. g., much worse than acetone peroxide) and it makes melt-casting it impractical for commercial applications.

Melt-cast ETN, if cooled down slowly over a period of 10–30 minutes, has a density of , detonation velocity of 8,040 m/s, and Pcj detonation pressure of about 300000 bar. Its brisance is far higher than that of Semtex (about 220000 bar, depending on brand). Mixtures of 50:50 PETN:ETN have P slightly above 300000 bar and detonation velocity above 8 km/s. This is close to the maximum of fielded military explosives like LX-10 or EDC-29 (about 370000 bar and close to 9 km/s).

ETN is often plasticized using PIB/synthetic oil binders (very comparable to the binder system in C4) or using liquid nitric esters. The PIB-based plastic explosives are nontoxic and completely comparable to C4 or Semtex with P of 200000-250000 bar, depending on density (influenced by crystal size, binder amount, and amount of final rolling). EGDN/ETN/NC systems are toxic to touch, quite sensitive to friction and impact, but generally slightly more powerful than C4 (P of about 250000 bar and E of ) and more powerful than Semtex (P of about 220000 bar and E below ) with P of about 250000-270000 bar and E of about . Note that explosion modeling software and experimental tests will yield absolute detonation pressures that can vary by 5% or more with the relative proportions being maintained. Erythritol tetranitrate can form eutectic mixtures with a variety of explosive compounds, including TNT, PETN, mannitol hexanitrate, and 1,3,5-trinitrobenzene.

Melt-cast ETN gives invalid results in the Hess test, i.e. the deformation is greater than 26 mm, with the lead cylinder being completely destroyed. Semtex 1A gives only 21 mm in the same test, i.e. melt-cast ETN is at least 20% more brisant than Semtex 1A.

Melt-cast ETN or high density/low inert content ETN plastic explosives are one of the materials on "watch-lists" for terrorism.

Oxygen balance

One positive characteristic of ETN that PETN does not possess is a positive oxygen balance, which means that ETN possesses more than enough oxygen in its structure to fully oxidize all of its carbon and hydrogen upon detonation. This can be seen in the schematic chemical equation below:

:

Whereas PETN decomposes to:

:

The carbon monoxide (CO) still requires oxygen to complete oxidation to carbon dioxide (). A detailed study of the decomposition chemistry of ETN has been recently elucidated.

Thus, for every two moles of ETN that decompose, one free mole of is released. This oxygen could be used to oxidize an added metal dust, or an oxygen-deficient explosive, such as TNT or PETN. The extra oxygen from the ETN oxidizes the carbon monoxide (CO) to carbon dioxide ():

:

Manufacture

Like other nitrated polyols, ETN is made by nitrating erythritol either through the mixing of concentrated sulfuric acid and a nitrate salt, or by using a mixture of sulfuric and nitric acid.

References

References

1. Erythritol tetranitrate was first synthesized by British chemist [[John Stenhouse]] (1809–1880) in 1849. He extracted the simple sugar erythritol (which he called "erythroglucin") from lichen and then studied its chemistry. See: John Stenhouse (1 January 1849) "Examination of the proximate principles of some of the lichens. Part II," ''Philosophical Transactions of the Royal Society (London)'', vol. 139, pages 393-401. Reprinted in German as: John von Stenhouse (1849) "Über die näheren Bestandtheile einige Flechten," Justus Liebigs ''Annalen der Chemie und Pharmacie'', vol. 70, no. 2, pages 218-228. Condensed version (in German): John Stenhouse (12 Sept. 1849) "Über die näheren Bestandtheile einige Flechten," ''Pharmaceutisches Centralblatt'', vol. 20, no. 40, [https://books.google.com/books?id=AaQ5AAAAcAAJ&pg=PA625 pages 625–628].
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