TKX-50

TKX-50
Names
IUPAC name
Dihydroxylammonium-5,5′-bistetrazolyl-1,1′-diolate
Other names
Dihydroxylammonium-5,5′-bistetrazolyl-1,1′-diolate, Dihydroxylammonium-5,5′-bistetrazolyl-1,1′-dioxide,
Identifiers
3D model (JSmol)
  • InChI=1S/C2N8O2.2H4NO/c11-9-1(3-5-7-9)2-4-6-8-10(2)12;2*1-2/h;2*2H,1H3/q-2;2*+1
    Key: UHTGTYVZCBKFMU-UHFFFAOYSA-N
  • [NH3+]O.[NH3+]O.[O-]N1N=NN=C1C2=NN=NN2[O-]
Properties
C2H8N10O4
Molar mass 236.15 g/mol
Appearance colorless crystals
Density 1.92 g/cm3
Explosive data
Shock sensitivity 20 J
Friction sensitivity 120 N
Detonation velocity 9698 m/s
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

TKX-50 is the chemical compound with the formula C2H8N10O4; it is a hydroxylammonium salt of 5,5′-bistetrazolyl-1,1′-diolate that forms colorless crystals, and it is a high-performing explosive with superior performance to RDX and HMX while being more resistant to mechanical stimuli. It is also considered an environmentally-friendly replacement for several conventional explosives.

It was invented by Niko Fischer, Dennis Fischer, Davin G. Piercey, Thomas M. Klapötke and Jörg Stierstorfer in Klapötke's research group at LMU Munich. Its development was funded by LMU Munich, the U.S. Army Research Laboratory (ARL), the Armament Research, Development and Engineering Center (ARDEC), the Strategic Environmental Research and Development Program (SERDP) and the Office of Naval Research (ONR).

As of 2014, the US Army was preparing it in 20 kg batches in order to evaluate it as an explosive.

Synthesis

The compound is prepared by reacting 5,5′-bistetrazolyl-1,1′-diol (BTO) with hydroxylamine. The starting compound BTO can be obtained relatively easily from glyoxal, hydroxylamine, chlorine, and sodium azide.

TKX-50 synthesis

Since the initial synthesis of TKX-50, multiple research groups have improved the synthesis to make it more suitable for mass production, including by adding protecting groups to make intermediates safer, and the United States Army Research Laboratory has performed multiple steps via a one-pot synthesis.

Characteristics

TKX-50 is a crystalline solid with no melting point. The compound occurs in two polymorphic crystal forms. At about 180 °C, a second-order phase transition with a small heat capacity change of about 0.3 J/mol·K is observed, resulting in a transformation from the low-temperature to a high-temperature crystal form. The crystal system changes from monoclinic with the space group P21/c to triclinic with the space group P1. The compound is thermally unstable. DSC measurements show an exothermic decomposition reaction above 215 °C with a latent heat of decomposition of −2200 kJ/kg and −520 kJ/mol, respectively. The standard enthalpy of formation based on combustion calorimetry measurements is 473 kJ/mol.

Explosive properties

TKX-50 has been found to lead to melt-cast formulations with higher performance than those with HMX. Its detonation velocity, Chapman–Jouguet detonation pressure, and density are also superior to RDX.

References

  1. 1 2 Badgujar, Dilip M.; Talawar, Mahadev B.; Mahulikar, Pramod P. (2017), "Review of Promising Insensitive Energetic Materials" (PDF), Central European Journal of Energetic Materials, vol. 14, no. 4, pp. 821–843, doi:10.22211/cejem/68905
  2. 1 2 Wilson, Elizabeth K. (10 September 2012). "Safer Explosives Still Pack a Punch". Chemical & Engineering News. Retrieved 21 January 2025.
  3. ↑ Fischer, Niko; Fischer, Dennis; Klapötke, Thomas M.; Pierceya, Davin G.; Stierstorfer, Jörg (2012), "Pushing the limits of energetic materials – the synthesis and characterization of dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate", Journal of Materials Chemistry, vol. 22, no. 38, pp. 20418–20422, doi:10.1039/C2JM33646D
  4. ↑ "Boom!".
  5. ↑ Fischer, N.; Klapötke, T.M.; Reymann, M.; Stierstorfer, J.: Nitrogen-Rich Salts of 1H,1'H-5,5'-Bitetrazole-1,1'-diol: Energetic Materials with High Thermal Stability in Eur. J. Inorg. Chem. 2013, 2167–2180, doi:10.1002/ejic.201201192.
  6. ↑ US patent 9296664, Thomas M. Klapötke, Niko Fischer, Dennis Fischer, Davin G. Piercey, Jörg Stierstorfer, Marius Reymann, "Energetic active composition comprising a dihydroxylammonium salt or diammonium salt of a bistetrazolediol", issued 2016-03-29
  7. ↑ Kwon, K.; Kim, S.; Lee, S.; Lee, W. H.: Safe and Scale-up-friendly Synthesis of TKX-50 in Propellants Explos. Pyrotech. 2025, e12073, doi:10.1002/prep.12073.
  8. ↑ US patent 9643937B1, Reddy Damavarapu, Raja Duddu, "One-pot process for preparation of ammonium and hydroxyl ammonium derivatives of bis 5,5′-tetrazole-1,1′-dihydroxide", issued 2017-05-09
  9. ↑ Zhipeng Lu, Xianggui Xue, Liya Meng, Qun Zeng, Yu Chi, Guijuan Fan, Hongzhen Li, Zengming Zhang, Fude Nie, Chaoyang Zhang: Heat-Induced Solid−Solid Phase Transformation of TKX-50 in J. Phys. Chem. C 121 (2017) 8262–8271, doi:10.1021/acs.jpcc.7b00086.
  10. ↑ Niu, Hu; Chen, Shusen; Shu, Qinghai; Li, Lijie; Jin, Shaohua (2017-09-15), "Preparation, characterization and thermal risk evaluation of dihydroxylammonium 5, 5′-bistetrazole-1, 1′-diolate based polymer bonded explosive", Journal of Hazardous Materials, vol. 338, pp. 208–217, doi:10.1016/j.jhazmat.2017.05.040, PMID 28558326
  11. ↑ Dilip Badgujar, Mahadev Talawar (2017), "Thermal and Sensitivity Study of Dihydroxyl Ammonium 5,5′-Bistetrazole-1,1′-diolate (TKX-50)-based Melt Cast Explosive Formulations", Propellants, Explosives, Pyrotechnics, vol. 42, no. 8, pp. 883–888, doi:10.1002/prep.201600168
  12. ↑ D. Fischer, V. Golubev, T. M. Klapötke, J. Stierstorfer: Synthesis and Characterization of Novel High-Nitrogen Secondary Explosives. In: Tagungsband die 21. Kalorimetrietage : Braunschweig, 27.-29. Mai 2015 / Veranstalter Gesellschaft für Thermische Analyse e. V., Physikalisch-Technische Bundesanstalt. ISBN 978-3-944659-02-2 (Abstract).
  13. ↑ Yu, Y.; Chen, S.; Li, T.; Jin, S.; Zhang, G.; Chen, M.; Li, L.: Study on a novel high energetic and insensitive munitions formulation: TKX-50 based melt cast high explosive in RSC Advances 2017, 31485-31492, doi:10.1039/C7RA05182D.