Acetone peroxide

Acetone peroxide (also called APEX) is an organic peroxide and a primary high explosive. It is produced by the reaction of acetone and hydrogen peroxide to yield a mixture of linear monomer and cyclic dimer, trimer, and tetramer forms. The trimer is known as triacetone triperoxide (TATP) or tri-cyclic acetone peroxide (TCAP). The dimer is known as diacetone diperoxide (DADP). Acetone peroxide takes the form of a white crystalline powder with a distinctive bleach-like odor (when impure) or a fruit-like smell when pure, and can explode powerfully if subjected to heat, friction, static electricity, concentrated sulfuric acid, strong UV radiation or shock. Until about 2015 explosives detectors were not set to detect non-nitrogenous explosives as most explosives used were nitrogen-based. Nitrogen-free TATP was used as the explosive in several terrorist bomb attacks since 2001. Acetone peroxide (specifically, triacetone triperoxide) was discovered in 1895 by Richard Wolffenstein. Wolffenstein combined acetone and hydrogen peroxide, and then he allowed the mixture to stand for a week at room temperature, during which time a small quantity of crystals precipitated, which had a melting point of 97 °C. In 1899 Adolf von Baeyer and Victor Villiger described the first synthesis of the dimer and described use of acids for the synthesis of both peroxides. Baeyer and Villiger prepared the dimer by combining potassium persulfate in diethyl ether with acetone, under cooling. After separating the ether layer, the product was purified and found to melt at 132–133 °C. They found that the trimer could be prepared by adding hydrochloric acid to a chilled mixture of acetone and hydrogen peroxide. By using the depression of freezing points to determine the molecular weights of the compounds, they also determined that the form of acetone peroxide that they had prepared via potassium persulfate was a dimer, whereas the acetone peroxide that had been prepared via hydrochloric acid was a trimer, like Wolffenstein's compound. Work on this methodology and on the various products obtained, was further investigated in the mid-20th century by Milas and Golubović. The chemical name acetone peroxide is most commonly used to refer to the cyclic trimer, the product of a reaction between two precursors, hydrogen peroxide and acetone, in an acid-catalyzed nucleophilic addition, although various further monomeric and dimeric forms are possible. Specifically, two dimers, one cyclic (C6H12O4) and one open chain (C6H14O4), as well as an open chain monomer (C3H8O4), can also be formed; under a particular set of conditions of reagent and acid catalyst concentration, the cyclic trimer is the primary product. A tetrameric form has also been described, under different catalytic conditions. The synthesis of tetrameric acetone peroxide has been disputed. Under neutral conditions, the reaction is reported to produce the monomeric organic peroxide. The most common route for nearly pure TATP is H2O2/acetone/HCl in 1:1:0.25 molar ratios, using 30% hydrogen peroxide. This product contains very little or none of DADP with some very small traces of chlorinated compounds. Product that contains large fraction of DADP can be obtained from 50% H2O2 using high amounts of conc. sulfuric acid as catalyst or alternatively with 30% H2O2 and massive amounts of HCl as a catalyst. The product made by using hydrochloric acid is regarded as more stable than the one made using sulfuric acid. It is known that traces of sulfuric acid trapped inside the formed acetone peroxide crystals lead to instability. In fact, the trapped sulfuric acid can induce detonation at temperatures as low as 50 °C, this is the most likely mechanism behind accidental explosions of acetone peroxide that occur during drying on heated surfaces.