|Molecular formula||C6H12O4 (dimer)
|Molar mass||148.157 g/mol (dimer)
222.24 g/mol (trimer)
|Appearance||White crystalline solid|
91 °C, 364 K, 196 °F
|Shock sensitivity||Very high / moderate when wet|
|Friction sensitivity||Very high / moderate when wet|
|Explosive velocity||5300 m/s
3.29 Miles per second
|Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)|
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 odor.
It is susceptible to heat, friction, and shock. However the instability is greatly altered by impurities. It is normally fairly stable when pure. It is not easily soluble in water. It is more stable and less sensitive when wet.
Acetone peroxide was discovered in 1895 by Richard Wolffenstein. He was the first chemist to use inorganic acids as catalysts. He was also the first researcher to receive a patent for using the peroxide as an explosive compound. In 1900 Bayer and Villiger described in the same journal the first synthesis of the dimer and also described use of acids for the synthesis of both peroxides. Information about these procedures including the relative proportions of monomer, dimer, and trimer is also available in an article by Milas and Golubović. 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.
Acetone peroxide has been used in various crimes and terrorist acts. It has also been the cause of accidental injuries. Due to its high susceptibility to accidental detonation by shock, friction, or sparks, acetone peroxide has earned the nickname "Mother of Satan" among certain Islamic militant groups.
"Acetone peroxide" most commonly refers to the cyclic trimer TCAP (tri-cyclic acetone peroxide, or tri-cyclo, C9H18O6) obtained by a reaction between hydrogen peroxide and acetone in an acid-catalyzed nucleophilic addition. The dimer (C6H12O4) and open monomer 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 larger crystals of the same peroxide.
Acetone peroxide is notable as a high explosive not containing nitrogen. This is one reason why it has become popular with terrorists, as it can pass through scanners designed to detect nitrogenous explosives.
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:
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."  But even in 1943 German researcher(s) described in the case of detonation of the trimer the formation of formaldehyde which is clearly a result of a fragmentation of primary formed oxyradicals. This result is in good agreement with the results of 60 years of the study of controlled decompositions in various organic peroxides. 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.
Due to the cost and ease with which the precursors can be obtained, acetone peroxide can be manufactured by those without the resources needed to manufacture or buy more sophisticated explosives. When the reaction is carried out without proper equipment the risk of an accident is significant. Simply mixing sulfuric acid, hydrogen peroxide, and acetone can create the substance. The mixture starts as a liquid that quickly crystallizes into a powder.
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 dimeric 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."
In reality, the acid-catalyzed peroxidation of acetone always produces a mixture of the 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 sensitive to initiation. Organic peroxides are sensitive, dangerous explosives; due to their sensitivity they are rarely used by well funded militaries. Even for those who synthesize explosives as a hobby there are far safer explosives with syntheses nearly as simple as that of acetone peroxide. It is commonly combined with nitrocellulose by dissolving the nitrocellulose in acetone and then mixing in the acetone peroxide and letting it dry, this results in a mixture that is both more stable and somewhat more powerful than acetone peroxide by itself. This mixture is commonly referred to as APNC.
Tetrameric acetone peroxide is more chemically stable (heating to 120°C for 4 hours), but despite this, it is still a very dangerous primary explosive. It can be prepared using tin(IV) chloride (without acid present) as a catalyst with up to 40% yield if radical inhibitor such as hydroquinone, or a chelator such as EDTA is added. 
Acetone peroxides are common and unwanted by-products of oxidation 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.
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-reinforced composites. 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.
Acetone peroxide can also occur accidentally, when suitable chemicals are mixed together, for example when methyl ethyl ketone peroxide is mixed with acetone while making fiberglass composites, and left to stand for some time, or when a mixture of peroxide and hydrochloric acid from printed circuit board etching 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.
TATP is relatively easy to make and has been used in various terrorist acts.
A 13-year-old student in Hong Kong was injured on March 28, 2009 when he tried to light some TATP powder provided by another 14-year-old boy. Police found six more bottles of TATP from his apartment. Police believe those bottles of TATP were homemade by the 14-year-old boy for curiosity's sake. Including the injured boy, 3 teenagers were later arrested on explosives possession charges.