Acetone peroxide

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Image:Acetone peroxide.png Acetone peroxide
3,3,6,6-tetramethyl-1,2,4,5-tetraoxane (dimer) 3,3,6,6,9,9-hexamethyl-1,2,4, 5,7,8-hexaoxacyclononane (trimer) IUPAC name
Chemical formula	C₆H₁₂O₄ (dimer) C₉H₁₈O₆ (trimer)
Molecular mass	148.157 g/mol (dimer) 222.24 g/mol (trimer)
Shock sensitivity	High
Friction sensitivity	High
Density	1.18 g/cm³
Explosive velocity	5300 m/s
RE factor	?
Melting point	91 °C
Autoignition temperature	Unknown
Appearance	White crystalline solid
CAS number	17088-37-8
PubChem	536100
SMILES	CC1(C)OOC(C)(C)OOC(C)(C)OO1 CC1(C)OOC(C)(C)OO1

Image:Acetone peroxide.jpg

Acetone peroxide (triacetone triperoxide, peroxyacetone, TATP, TCAP) is an organic peroxide and a primary high explosive. It takes the form of a white crystalline powder with a distinctive acrid smell.

It is highly susceptible to heat, friction, and shock. For its instability, it has been called the "Mother of Satan".<ref>July 15, 2005 TimesOnline</ref> It has perhaps sprung into notoriety due to its alleged use in the July 2005 London bombings and has also been reported as the explosive favored by suspects arrested on August 10, 2006 who allegedly intended to destroy airplanes flying from the United Kingdom to the United States.<ref>http://www.time.com/time/nation/article/0,8599,1225453,00.html</ref>

Acetone peroxide was discovered in 1895 by R. Wolffenstein.<ref>Wolffenstein, R (1895). "Über Die Einwirkung von Wasserstoffsuperoxyd auf Aceton und Mesityloxyd". Chemische Berichte 28: 2265.</ref> Information about it including the relative proportions of monomer, dimer, and trimer is also available in the Journal of the American Chemical Society 81, 6461 (1959). Other sources include crystal structure and 3d analysis in "The Chemistry of Peroxides" edited by Saul Patai (pp. 396–7), as well as the "Textbook of Practical Organic Chemistry" by Vogel.

1 Chemistry
2 Industrial occurrence
3 Accidental byproduct
4 Terrorism
5 References
6 See also
7 External links

[edit] Chemistry

Also known as "peroxyacetone", acetone peroxide most commonly refers to the cyclic trimer TCAP (tri-cyclic acetone peroxide, or tri-cyclo), also called triacetone triperoxide (TATP), obtained by a reaction between hydrogen peroxide and acetone in an acid-catalyzed nucleophilic addition.<ref>Megalomania's Method of Making Acetone Peroxide. Megalomania's Controversial Chem Lab (January 31, 2004).</ref> The cyclic dimer (C₆H₁₂O₄) and open monomer and dimer are also formed, but under proper conditions the cyclic trimer is the primary product. A tetrameric form was also described. In mildly acidic or neutral conditions, the reaction is much slower and produces more monomeric organic peroxide than the reaction with a strong acid catalyst. Due to significant strain of the chemical bonds in the dimer and especially the monomer, they are even more unstable than the trimer.

At room temperature, the trimeric form slowly sublimes, reforming as the less stable, more sensitive dimer.

TCAP generally burns when ignited, unconfined, in quantities less than about 2 grams. More than 2 grams will usually detonate when ignited; smaller quantities might detonate when even slightly confined. Completely dry TCAP is much more prone to detonation than the fresh product still wetted with water or acetone. The oxidation that occurs when burning is:

2 C₉H₁₈O₆ + 21 O₂ → 18 H₂O + 18 C O₂

Theoretical examination of the explosive decomposition of TCAP, in contrast, predicts in "formation of acetone and ozone as the main decomposition products and not the intuitively expected oxidation products."<ref name=http://www.technion.ac.il/~keinanj/pub/122.pdf>J. Am. Chem. Soc. 2005, 1146–1159</ref> It is the rapid creation of gas from a solid that creates the explosion. Very little heat is created by the explosive decomposition of TCAP. Recent research describes TCAP decomposition as an entropic explosion.

The extreme shock, heat, and friction sensitivity are due to the instability of the molecule. Big crystals, found in older mixtures, are more dangerous, as they are easier to shatter — and initiate — than small ones.

Many people have been killed or permanently injured by accidents with acetone peroxide. It is widely used by people who want to make homemade explosives because of its low cost and ease of manufacture. They may be unaware of its extreme sensitivity; or they make it anyway because it is cheap and can be made in a refrigerator.

There is a common myth that the only "safe" acetone peroxide is the trimer, made at low temperatures:

"The mixture must be kept below 10 degrees Celsius. If the crystals form at this temperature, it forms the isomer called tricycloacetone peroxide, which is relatively stable and safe to handle. If the crystals form above this temperature, the dimerric form, called dicycloacetone peroxide. This isomer is much more unstable, and could go off at the touch, making it not safe enough to be considered a practical explosive. As long as the temperature is kept below 10 degrees Celsius, then there is little to worry about."<ref>http://www.totse.com/en/bad_ideas/ka_fucking_boom/162660.html]</ref>

In reality, the acid-catalyzed peroxidation of acetone always produces a mixture of dimeric and trimeric forms.

The trimer is the more stable form, but not much more so than the dimer. All forms of acetone peroxide are very sensitive to initiation. Organic peroxides are sensitive, dangerous explosives. The military does not use them because there are many much better alternatives. Even for people who synthesize homemade explosives, there are many far safer alternatives. Even nitroglycerin is not nearly as sensitive as acetone peroxide.

[edit] Industrial occurrence

Acetone peroxides are common and unwanted by-products of oxidate reactions, eg. those used in phenol syntheses. Due to their explosivity, they are hazardous. Numerous methods are used to reduce their production - shifting the pH to more alkaline, adjusting the reaction temperature, or adding a soluble copper(II) compound.<ref>Destruction of acetone peroxide patent</ref>

Acetone peroxide and benzoyl peroxide are used as flour bleaching agents to bleach and "mature" flour.

Ketone peroxides, including acetone peroxide, methyl ethyl ketone peroxide, and benzoyl peroxide, find applications as initiators for polymerization reactions of eg. silicone or polyester resins, often encountered when making fiberglass. For these uses, the peroxides are typically in the form of a dilute solution in an organic solvent, however, even commercial products with higher concentrations of organic peroxides can form crystals around the lid when older, making the can shock-sensitive. Methyl ethyl ketone is more common for this purpose, however, as it is stable in storage.

[edit] Accidental byproduct

Acetone peroxide can also occur accidentally, when suitable chemicals are mixed together. For example, when methyl ethyl ketone peroxide is mixed with acetone when making fiberglass, and left to stand for some time, or when a mixture of peroxide and hydrochloric acid from printed circuit board etching (the FeCl₃ method is less smelly, more accurate, but slower) is mixed with waste acetone from cleaning the finished board and allowed to stand. While amounts obtained this way are typically much smaller than from intentional production, they are also less pure and prepared without cooling, and hence very unstable.

It is also a hazardous by-product of isosafrole oxidation in acetone, a step in illicit synthesis of MDMA.

[edit] Terrorism

TATP has been identified in explosive devices in a number of cases involving jihadist terrorists. Richard Reid, who attempted to down American Airlines Flight 63 with a bomb concealed in his shoe, employed a device containing plastic explosive with a TATP trigger.<ref>http://www.guardian.co.uk/worldlatest/story/0,,-6007751,00.html</ref> It is also believed that acetone peroxide was used as the explosive in the 7 July 2005 London bombings.<ref>http://observer.guardian.co.uk/uk_news/story/0,,1769440,00.html</ref> On September 5, 2006, homemade TATP was found during the arrest of seven suspected terrorists in Vollsmose, a neighborhood in the Danish city Odense.<ref>http://politiken.dk/indland/article171600.ece</ref> In addition, the participants in the 2006 transatlantic aircraft plot may have planned to use TATP as the liquid bombs, mixed in airplane lavatories, that would destroy U.S. airliners flying from London to the United States.<ref>http://www.rsc.org/chemistryworld/News/2006/August/11080602.asp</ref> Nevertheless, some reports suggest that such bombs would not have been very effective, due to the supplies needed, the smell mixing would create, and the time it would take to prepare without drawing suspicion from passengers and the flight crew.<ref>http://www.theregister.co.uk/2006/08/17/flying_toilet_terror_labs/</ref>