PETN

# Overview
Pentaerythritol tetranitrate (PETN), also known as PENT, PENTA, TEN, corpent, penthrite (orrarely and primarily in Germanas nitropenta), is the nitrate ester of pentaerythritol, and is structurally very similar to nitroglycerin. Penta refers to the five carbon atoms of the neopentane skeleton.
PETN is best known as an explosive. It is one of the most powerful high explosives known, with a relative effectiveness factor of 1.66.
PETN mixed with a plasticizer forms a plastic explosive. As a mixture with RDX and other minor additives, it forms another plastic explosive called Semtex as well. The compound was discovered in the bombs used by the 2001 Shoe Bomber, in the 2009 Christmas Day bomb plot, and in the 2010 cargo plane bomb plot. On 7 September 2011, a bomb suspected to have used PETN exploded near the High Court of Delhi in India claiming 13 lives and injuring more than 70.
It is also used as a vasodilator drug to treat certain heart conditions, such as for management of angina.

# History
Penthrite was first synthesized in 1891 by Bernhard Tollens and P. Wigand by nitration of pentaerythritol. The production of PETN started in 1912, when it was patented by the German government. PETN was used by the German Army in World War I.

# Properties
PETN is practically insoluble in water (0.01 g/100 ml at 50 C), weakly soluble in common nonpolar solvents such as aliphatic hydrocarbons (like gasoline) or tetrachloromethane, but soluble in some other organic solvents, particularly in acetone (about 15 g/100 g of the solution at 20 C, 55 g/100 g at 60 C) and dimethylformamide (40 g/100 g of the solution at 40 C, 70 g/100 g at 70 C). PETN forms eutectic mixtures with some liquid or molten aromatic nitro compounds, e.g. trinitrotoluene (TNT) or tetryl. Due to its highly symmetrical structure, PETN is resistant to attack by many chemical reagents; it does not hydrolyze in water at room temperature or in weaker alkaline aqueous solutions. Water at 100 C or above causes hydrolysis to dinitrate; presence of 0.1% nitric acid accelerates the reaction. Addition of TNT and other aromatic nitro derivatives lowers thermal stability of PETN.
The chemical stability of PETN is of interest, because of the use of PETN in aging stockpiles of weapons. A review has been published.  Neutron radiation degrades PETN, producing carbon dioxide and some pentaerythritol dinitrate and trinitrate. Gamma radiation increases the thermal decomposition sensitivity of PETN, lowers melting point by few degrees Celsius, and causes swelling of the samples. Like other nitrate esters, the primary degradation mechanism is the loss of nitrogen dioxide; this reaction is autocatalytic. Studies were performed on thermal decomposition of PETN.
In the environment, PETN undergoes biodegradation. Some bacteria denitrate PETN to trinitrate and then dinitrate, which is then further degraded.  PETN has low volatility and low solubility in water, and therefore has low bioavailability for most organisms. Its toxicity is relatively low, and its transdermal absorption also seems to be low.  It poses a threat for aquatic organisms. It can be degraded to pentaerythritol by iron metal.

# Production
Production is by the reaction of pentaerythritol with concentrated nitric acid to form a precipitate which can be recrystallized from acetone to give processable crystals.
Variations of a method first published in a US Patent 2,370,437 by Acken and Vyverberg (1945 to Du Pont) forms the basis of all current commercial production.
PETN is manufactured by numerous manufacturers as a powder about the consistency of fine popcorn salt, or together with nitrocellulose and plasticizer as thin plasticized sheets (e.g. Primasheet 1000 or Detasheet). PETN residues are easily detectable in hair of people handling it. The highest residue retention is on black hair; some residues remain present even after washing.

# Medical Use
Like nitroglycerin (glyceryl trinitrate) and other nitrates, PETN is also used medically as a vasodilator in the treatment of heart conditions. These drugs work by releasing the signaling gas nitric oxide in the body. The heart medicine Lentonitrat is nearly pure PETN.
Monitoring of oral usage of the drug by patients has been performed by determination of plasma levels of several of its hydrolysis products, pentaerythritol dinitrate, pentaerythritol mononitrate and pentaerythritol, in plasma using gas chromatography-mass spectrometry.

# See Also
- Erythritol tetranitrate
- Pentaerythritol
- RDX