Pentaerythrite Tetranitrate

Penthrite was first synthesized in 1891 by Tollens and Wiegand by nitration of pentaerythritol. In 1912, after being patented by the German government, the production of PETN started. PETN was used by the German army in World War I. PETN is also one of the ingredients in Semtex plastic explosive. PETN was the explosive chosen by Richard Reid, which could have been used to blow up a 767 traveling from Paris to Miami if he wasn't stopped first.

IUPAC NAME: [3-nitrooxy-2,2-bis(nitrooxymethyl)propyl] nitrate
OTHER NAME: PETN, penta, niperyth, penthrit

Four equivalents of formaldehyde in warm aqueous solution in the presence of calcium hydroxide react with one equivalent of acetaldehyde to form pentaerythrite. Three of the four react with the three α-hydrogens of the acetaldehyde, the fourth acts as a reducing agent, converts the -CHO group to -CH2-OH, and is itself oxidized to formic acid[20] .

The name, pentaerythrite, indicates that the substance contains five carbon atoms and (like erythrite) four hydroxyI groups. In commerciaI practice the reaction is carried out at 65-70°C. After 2 hours at this temperature, the calcium is precipitated by means of sulfuric acid, the mixture is filtered, and the filtrate is concentrated and crystal1ized by evaporation in vacuum. Pentaerythrite crystallizes from water in white tetragonai crystaIs, m.p. 253°C. One part requires 18 parts of water at 15°C for its solution.
PETN may be prepared, according to Naoum, by adding 100 grams of finely powdered pentaerythrite to 400 cc. of nitric acid (1.52) while the temperature is maintained between 25°C and 30°C by efficient cooling. Toward the end of the nitration a certain amount of the tetranitrate crystallizes out. The separation of the product is completed by the graduaI addition of 400 cc. of concentrated sulfuric acid (1.84) while the stirring and cooling are continued. The mixture is not drowned, but the crude PETN (85-90% of the theory) is filtered off directly, and washed first with 50% sulfuric acid and then with water. It still contains some occluded acid and is purified, according to Nao¯m, by dissolving in hot acetone to which a Iittle ammonium carbonate is added, and filtering the hot solution into twice its volume of 90% alcohol by which the PETN is precipitated in fine needles.
Pentaerythrite may also be nitrated satisfactoriIy, and probably in better yield, without the use of sulfuric acid and with the use of nitric acid from which the nitrous acid has been removed. Pentaerythrite tetranitrate is the most stable and the Ieast reactive of the explosive nitric esters. It shows no trace of decomposition if stored for a very long time at 100°C. While nitrocellulose is destroyed within a few minutes by boiling with a 2.5% solution of caustic soda, PETN requires several hours for its complete decomposition. Ammonium sulfide solution attacks PETN slowly at 50°C, and a boiling solution of ferrous chloride decomposes it fairly rapidly. It does not reduce Fehling's solution even on boiling, and differs in this respect from erythrite tetranitrate. PETN does not take fire from the spit of a fuse. If a small quantity is submitted to the action of a flame, it melts and takes fire and burns quietly with a slightly luminous flame without smoke. Above 100°C it begins to show appreciable volatility, and at 140-145°C, or at temperatures slightly above its melting point, it shows red fumes within half an hour. It infiames spontaneously at about 210°C. It is relatively insensitive to friction but makes a loud crackling when rubbed in a rough porcelain mortar. It may be exploded readily by pounding with a carpenter's hammer on a concrete floor.
PETN is extraordinarily sensitive to initiation. It is detonated by 0.01 gram of lead azide, whereas tetryl requires 0.025 gram of lead azide for its certain detonation. This sensitivity and its great brisance combine to make PETN exceptionally serviceable in compound detonators.
Under high pressure powdered PETN agglomerates to a mass which has the appearance of porcelain, but which, when broken up into grains, is a very powerful smokeless powder functioning satisfactorily with the primers which are commonly used in small arms ammunition. The powder is hot and unduly erosive, but cooler powders have been prepared by incorporating and compressing PETN in binary or in ternary mixtures with TNT, nitroguanidine, and guanidine picrate. A mixture of PETN with guanidine picrate is less sensitive to heat and to shock than ordinary colloided smokeless powder, and is stable at all temperatures which are likely to be encountered. PETN does not colloid with nitrocellulose. It dissolves readily in warm trinitrotoluene, and mixtures may be prepared which contain 65% or more of PETN. The richer mixtures may be used as propellent powders, The less-rich mixtures are brisant and powerful high explosives comparable in their behavior and effects to TNB.
Stettbacher in 1931 described several dynamite-like explosives which contained both PETN and nitroglycerin. He called them by the generaI name of Penthrinit, and described simple penthrinit, gelatin penthrinit, and ammonpenthrinit.