Pentaerythritol tetranitrate (PETN)

English

Bernhard Christian Gottfried Tollens was a German chemist. In 1891, he and a student (P. Wigand) created the compound pentaerythritol.

Pentaerythrytol

Pentaerythritol is similar to glycerin, but instead of having three carbons and three OH groups, it has five carbons arranged symmetrically like a child's toy jack, with four OH groups attached to the four terminal carbons.

In looking for a better explosive than nitroglycerin, it makes sense to start with something similar to glycerin, but with more carbon, since nitroglycerin has a positive oxygen balance, and the extra fuel would bring the balance closer to zero. Nitroglycerin is what chemists call an ester. An ester is a combination of an acid, such as nitric acid, and an alcohol, which is a carbon chain with an OH group attached. The acid, in this case HNO3 (nitric acid) loses its hydrogen to the OH group, to make HOH (water, or H2O). The remaining part of the acid attaches to the carbon that used to have the OH group attached.

By slowly pouring pentaerythritol powder into an ice-cold mixture of concentrated sulfuric and nitric acids, we can attach four NO3 groups to the legs of the molecule. This is exactly what was done at the German munitions factory of Rheinisch-Westfälische Sprengstoff A.G. in Cologne, Germany in 1894.

PETN is one of the most explosive compounds known. It is 1.66 times more explosive than TNT.

In 1912, the German government patented a better way to produce it, just in time for use in World War I (1914 to 1918).

PETN degrades more slowly than nitroglycerin or nitrocellulose, but it is still less stable than TNT. It is less shock sensitive than nitroglycerin, but more sensitive than TNT. For these reasons, it is often mixed with TNT or other explosives, resulting in a mix that has the high brisance of PETN, but is less sensitive and stores better.

PETN

PETN is the ingredient used in primer cord, an explosive string that is used to set off other explosive charges. Going by the name of primacord, or detcord, it is a plastic tube full of PETN. By connecting separately spaced charges with detcord, the extremely high detonation velocity of the PETN leads to near-simultaneous detonation of all the charges.

A few wraps of detcord around a tree can cut it down much faster than a chainsaw, and it is used this way militarily by engineering teams to clear a path for mechanized equipment. In rubberized sheet form with nitrocellulose, PETN makes up Primasheet and Detasheet. These are used for explosive welding applications, since they can be wrapped around the objects to be welded together.

A mixture of 50% PETN and 50% TNT is called Pentolite. Pentolite can be cast like TNT, and is more stable than pure PETN, while still having a detonation velocity between 7,400 and 7,800 meters per second. It is used as a booster explosive for harder to detonate explosives like ammonium nitrate based mixtures.

PETN is often phlegmatized (made less sensitive by adding less explosive or non-explosive materials) by paraffin or wax, or by polymers such as rubber or silicone to make plastic explosives. In this form, it can be used in some of the smaller caliber artillery shells.

Because PETN has a low vapor pressure (it does not vaporize easily), it is more difficult to detect, by bomb detector equipment or by bomb sniffing dogs. Combined with its high power and ease of manufacture, this has made it a favorite of several infamous terror plots.

Richard Reid, the so-called "shoe bomber", tried to use PETN detonated by TATP to bring down American Airlines Flight 63. An al-Qaeda suicide plot to assassinate Saudi Prince Muhammad bin Nayef almost succeeded with a bomb inserted in the rectum of the suicide bomber. He successfully detonated the bomb, but the target survived. The Nigerian "Underwear Bomber" tried unsuccessfully to detonate a PETN bomb sewn into his underwear by injecting it with a syringe of liquid believed to be nitroglycerin. A small fire resulted instead of the planned detonation. PETN printer cartridges were found on a Dubai flight, thanks to intelligence work (not by bomb detection). Had they detonated, they would have been more than powerful enough to down the plane.

Like nitroglycerin, PETN is a vasodilator, and can be used to treat angina. In nearly pure form in the drug Lentonitrat, it can be sprayed under the tongue to relieve symptoms and quickly lower blood pressure.