Entropic explosion

An entropic explosion is an explosion in which the reactants undergo a large change in volume without releasing a large amount of heat. The chemical decomposition of triacetone triperoxide (TATP) is an example of an entropic explosion.[1] It is not a thermochemically highly favored event because little energy is generated in chemical bond formation in reaction products, but rather involves an entropy burst, which is the result of formation of one ozone and three acetone gas phase molecules from every molecule of TATP in the solid state.[2][3][4][5]

This hypothesis has been questioned as opposing to other theoretical investigations as well as actual measurements of the detonation heat of TATP. Experiments have shown that the explosion heat of TATP is about 2800 kJ/kg (about 70% of TNT) and that it acts as a usual explosive, producing a mix of hydrocarbons, water and carbon oxides upon detonation.[6]

The authors of the 2005 Dubnikova et al. study confirm that a final redox reaction (combustion) of ozone, oxygen and reactive species into water, various oxides and hydrocarbons takes place within about 180 ps after the initial reaction - within about a micron of the detonation wave. Crystals of TATP ultimately reach a temperature of 2300 K and pressure of 80 kbar[7]

References
  1. Dubnikova, Faina; Kosloff, Ronnie; Almog, Joseph; Zeiri, Yehuda; Boese, Roland; Itzhaky, Harel; Alt, Aaron; Keinan, Ehud (2005). "Decomposition of Triacetone Triperoxide is an Entropic Explosion". Journal of the American Chemical Society. 127 (4): 1146–59. doi:10.1021/ja0464903. PMID 15669854.
  2. Dubnikova, Faina; Kosloff, Ronnie; Yehuda, Zeiri (2006). Schubert, Hitmar; Kuznetsov, Audrey (eds.). Rational Detection Schemes for TATP NATO Advanced Research Workshop. Netherlands: Springer. pp. 111–112. ISBN 978-1402048869. Retrieved 6 February 2017."The calculated thermal decomposition pathway of the TATP molecule was a complicated multistep process with several highly reactive intermediates, including singlet molecular oxygen and various biradicals. Of note, the calculations predict the formation of acetone and ozone as the main decomposition products and not the intuitively expected oxidation products. The key conclusion from this study is that the explosion of TATP is not a thermochemically highly favored event. Rather, the explosion involves entropy burst, which is the result of the formation of 4 gas-phase molecules from every molecule of TATP in the solid state. Quite unexpectedly, the 3 isopropylidene units of the TATP molecule do not play the role of fuel that can be oxidized and release energy during the explosion. Instead, these units function as molecular scaffolds that hold the 3 peroxide units close together spatially in the appropriate orientation for the decomposition chain reaction."
  3. "In the Media | Scripps Research". Archived from the original on November 5, 2005. Retrieved July 17, 2005.
  4. http://arutzsheva.com/news.php3?id=75139%5B%5D
  5. "Archived copy" (PDF). Archived from the original (PDF) on 2011-05-14. Retrieved 2005-07-17.CS1 maint: archived copy as title (link)
  6. Sinditskii, V.P; Kolesov, V.I; Egorshev, V.Yu; Patrikeev, D.I; Dorofeeva, O.V (2014). "Thermochemistry of cyclic acetone peroxides". Thermochimica Acta. 585: 10–15. doi:10.1016/j.tca.2014.03.046.
  7. Van Duin, Adri C. T; Zeiri, Yehuda; Dubnikova, Faina; Kosloff, Ronnie; Goddard, William A (2005). "Atomistic-Scale Simulations of the Initial Chemical Events in the Thermal Initiation of Triacetonetriperoxide". Journal of the American Chemical Society. 127 (31): 11053–62. doi:10.1021/ja052067y. PMID 16076213.


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