Hexanitrohexaazaisowurtzitane

Hexanitrohexaazaisowurtzitane, also called HNIW and CL-20, is a polycyclic nitroamine explosive with the formula C₆H₆N₁₂O₁₂. It has a better oxidizer-to-fuel ratio than conventional HMX or RDX. It releases 20% more energy than traditional HMX-based propellants.

Hexanitrohexaazaisowurtzitane

Partially condensed, stereo, skeletal formula of hexanitrohexaazaisowurtzitane Ball and stick model of hexazaisowurtzitane
Names
IUPAC name 2,4,6,8,10,12-Hexanitro-2,4,6,8,10,12-hexaazatetracyclo[5.5.0.03,11.05,9]dodecane
Other names CL-20 Hexanitrohexaazaisowurtzitane 2,4,6,8,10,12-Hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane Octahydro-1,3,4,7,8,10-hexanitro-5,2,6-(iminomethenimino)-1H-imidazo[4,5-b]pyrazine HNIW
Identifiers
CAS Number	135285-90-4 Y
3D model (JSmol)	Interactive image
Abbreviations	CL-20, HNIW
ChEBI	CHEBI:77327 N
ChemSpider	8064994 Y 9223599 (3R,9R)-dodec Y 9594121 (3R,5S,9R,11S)- dodec Y
ECHA InfoCard	100.114.169
PubChem CID	9889323 11048432 (3R,9R)-dodec 11419235 (3R,5S,9R,11S)- dodec
UNII	RQM82X0CL7 Y
CompTox Dashboard (EPA)	DTXSID90873482
InChI InChI=1S/C6H6N12O12/c19-13(20)7-1-2-8(14(21)22)5(7)6-9(15(23)24)3(11(1)17(27)28)4(10(6)16(25)26)12(2)18(29)30/h1-6H Y Key: NDYLCHGXSQOGMS-UHFFFAOYSA-N Y
SMILES [O-][N+](=O)N1C2C3N(C4C(N3[N+]([O-])=O)N(C(C1N4[N+]([O-])=O)N2[N+]([O-])=O)[N+]([O-])=O)[N+]([O-])=O
Properties
Chemical formula	C 6N 12H 6O 12
Molar mass	438.1850 g mol−1
Density	2.044 g cm−3
Explosive data
Detonation velocity	9,500 m/s
RE factor	1.9
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

History and use

In the 1980s, CL-20 was developed by the China Lake facility, primarily to be used in propellants.^[1]

While most development of CL-20 has been fielded by the Thiokol Corporation, the US Navy (through ONR) has also been interested in CL-20 for use in rocket propellants, such as for missiles, as it has lower observability characteristics such as less visible smoke.^[2]

Thus far, CL-20 has only been used in the AeroVironment Switchblade 300 “kamikaze” drone, but is undergoing testing for use in the Lockheed Martin [LMT] AGM-158C Long Range Anti-Ship Missile (LRASM) and AGM-158B Joint Air-to-Surface Standoff Missile-Extended Range (JASSM-ER).^[3]

The Indian Armed Forces have also looked into CL-20.^[4]

The Taiwanese National Chung-Shan Institute of Science and Technology innaugerated a CL-20 production facility in 2022 with reported integration into the HF-2 and HF-3 product lines.^[5]

Synthesis

Synthesis of CL20

First, benzylamine (1) is condensed with glyoxal (2) under acidic and dehydrating conditions to yield the first intermediate compound.(3). Four benzyl groups selectively undergo hydrogenolysis using palladium on carbon and hydrogen. The amino groups are then acetylated during the same step using acetic anhydride as the solvent. (4). Finally, compound 4 is reacted with nitronium tetrafluoroborate and nitrosonium tetrafluoroborate, resulting in HNIW.^[6]

Cocrystals

In August 2011, Adam Matzger and Onas Bolton published results showing that a cocrystal of CL-20 and TNT had twice the stability of CL-20—safe enough to transport, but when heated to 136 °C (277 °F) the cocrystal may separate into liquid TNT and a crystal form of CL-20 with structural defects that is somewhat less stable than CL-20.^[7][8]

In August 2012, Onas Bolton et al. published results showing that a cocrystal of 2 parts CL-20 and 1 part HMX had similar safety properties to HMX, but with a greater firing power closer to CL-20.^[9][10]

Polymeric derivatives

In 2017, K.P. Katin and M.M. Maslov designed one-dimensional covalent chains based on the CL-20 molecules.^[11] Such chains were constructed using CH
₂ molecular bridges for the covalent bonding between the isolated CL-20 fragments. It was theoretically predicted that their stability increased with efficient length growth. A year later, M.A. Gimaldinova and colleagues demonstrated the versatility of CH
₂ molecular bridges.^[12] It is shown that the use of CH
₂ bridges is the universal technique to connect both CL-20 fragments in the chain and the chains together to make a network (linear or zigzag). It is confirmed that the increase of the effective sizes and dimensionality of the CL-20 covalent systems leads to their thermodynamic stability growth. Therefore, the formation of CL-20 crystalline covalent solids seems to be energetically favorable, and CL-20 molecules are capable of forming not only molecular crystals but bulk covalent structures as well. Numerical calculations of CL-20 chains and networks' electronic characteristics revealed that they were wide-bandgap semiconductors.^[11][12]

See also

• 2,4,6-Tris(trinitromethyl)-1,3,5-triazine
• 4,4’-Dinitro-3,3’-diazenofuroxan (DDF)
• Hexanitrobenzene (HNB)
• Heptanitrocubane (HNC)
• HHTDD
• Octaazacubane (N8)
• Iceane (Wurtzitane)
• Octanitrocubane (ONC)
• RE factor
• TEX (explosive)

References

1. Kadam, Tanmay (2023-03-11). "Pioneered By The US, China 'Racing Ahead' Of Its Arch Rival In 'CL-20' Tech That Propels PLA's Deadly Missiles". Eurasian Times.
2. Yirka, Bob (9 September 2011). "University chemists devise means to stabilize explosive CL-20". Physorg.com. Archived from the original on 25 January 2021. Retrieved 8 July 2012.
3. Wolfe, Frank (2023-03-28). "CL-20 Used in Switchblade 300, May See Wider Use in JASSM-ER, LRASM, Other Munitions". Defense Daily. Retrieved 2024-04-26.
4. https://pib.gov.in/newsite/PrintRelease.aspx?relid=67872 ^{[bare URL]}
5. Tien-pin, Lo; Chung, Jake (6 July 2024). "Institute develops powerful explosive". taipeitimes.com. Taipei Times. Retrieved 7 July 2024.
6. Nair, U. R.; Sivabalan, R.; Gore, G. M.; Geetha, M.; Asthana, S. N.; Singh, H. (2005). "Hexanitrohexaazaisowurtzitane (CL-20) and CL-20-based formulations (review)". Combust. Explos. Shock Waves. 41 (2): 121–132. doi:10.1007/s10573-005-0014-2. S2CID 95545484.
7. Bolton, Onas (2011). "Improved Stability and Smart-Material Functionality Realized in an Energetic Cocrystal". Angewandte Chemie International Edition. 50 (38): 8960–8963. doi:10.1002/anie.201104164. hdl:2027.42/86799. PMID 21901797.
8. "Things I Won't Work With: Hexanitrohexaazaisowurtzitane". 11 November 2011. Archived from the original on 2015-09-03. Retrieved 2016-01-04.
9. Bolton, Onas (2012). "High Power Explosive with Good Sensitivity: A 2:1 Cocrystal of CL-20:HMX". Crystal Growth & Design. 12 (9): 4311–4314. doi:10.1021/cg3010882.
10. "Powerful new explosive could replace today's state-of-the-art military explosive". spacewar.com. 2012-09-06. Archived from the original on 2012-09-09.
11. Katin, Konstantin P.; Maslov, Mikhail M. (2017). "Toward CL-20 crystalline covalent solids: On the dependence of energy and electronic properties on the effective size of CL-20 chains". Journal of Physics and Chemistry of Solids. 108: 82–87. arXiv:1611.08623. Bibcode:2017JPCS..108...82K. doi:10.1016/j.jpcs.2017.04.020. S2CID 100118824.
12. Gimaldinova, Margarita A.; Maslov, Mikhail M.; Katin, Konstantin P. (2018). "Electronic and reactivity characteristics of CL-20 covalent chains and networks: a density functional theory study". CrystEngComm. 20 (30): 4336–4344. doi:10.1039/c8ce00763b.

Further reading

• Bolton, Onas; Adam J. Matzger (September 12, 2011). "Improved Stability and Smart-Material Functionality Realized in an Energetic Cocrystal". Angewandte Chemie. 123 (38): 9122–9125. Bibcode:2011AngCh.123.9122B. doi:10.1002/ange.201104164. hdl:2027.42/86799. PMID 21901797.
• Lowe, Derek (11 November 2011) "Things I won't work with: Hexanitrohexaazaisowurtzitane"