Hexanitrohexaazaisowurtzitane, also called HNIW and CL-20, is a polycyclic

nitroamine Nitroamines are organic compounds containing a nitro group bonded to an amine. The parent inorganic compound, where R1 = R2 = H, is nitramide Nitramide is a chemical compound with the molecular formula H2NNO2. Organyl derivatives of nitramide, ...

explosive with the formula C₆H₆N₁₂O₁₂. In the 1980s, CL-20 was developed by the

China Lake Naval Air Weapons Station China Lake is a United States military facility in California. China Lake may also refer to: Places in the United States *China Lake, Kern County, California, an unincorporated community named for a nearby dry lake *Chi ...

facility, primarily to be used in

propellant A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or other motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicles, the e ...

s. It has a better

oxidizer An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxid ...

-to-

fuel A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work. The concept was originally applied solely to those materials capable of releasing chemical energy but ...

ratio than conventional HMX or

RDX RDX (abbreviation of "Research Department eXplosive") or hexogen, among other names, is an organic compound with the formula (O2N2CH2)3. It is a white solid without smell or taste, widely used as an explosive. Chemically, it is classified as a ...

. It releases 20% more energy than traditional HMX-based propellants, and is widely superior to conventional high-energy propellants and explosives. While most development of CL-20 has been fielded by the

Thiokol Corporation Thiokol (variously Thiokol Chemical Corporation(/Company), Morton Thiokol Inc., Cordant Technologies Inc., Thiokol Propulsion, AIC Group, ATK Thiokol, ATK Launch Systems Group; finally Orbital ATK before becoming part of Northrop Grumman) was an ...

, the

US Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage of ...

(through ONR) has also been interested in CL-20 for use in

rocket propellant Rocket propellant is the reaction mass of a rocket. This reaction mass is ejected at the highest achievable velocity from a rocket engine A rocket engine uses stored rocket propellants as the reaction mass for forming a high-speed propuls ...

s, such as for

missiles In military terminology, a missile is a guided airborne ranged weapon capable of self-propelled flight usually by a jet engine or rocket motor. Missiles are thus also called guided missiles or guided rockets (when a previously unguided rocket i ...

, as it has lower observability characteristics such as less visible smoke. CL-20 has not yet been fielded in any production weapons system, but is undergoing testing for stability, production capabilities, and other weapons characteristics.

Synthesis

First,

benzylamine Benzylamine is an organic chemical compound with the condensed structural formula C6H5CH2NH2 (sometimes abbreviated as PhCH2NH2 or BnNH2). It consists of a benzyl group, C6H5CH2, attached to an amine functional group, NH2. This colorless water ...

(1) is condensed with

glyoxal Glyoxal is an organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of ...

(2) under acidic and dehydrating conditions to yield the first intermediate compound.(3). Four benzyl groups selectively undergo

hydrogenolysis Hydrogenolysis is a chemical reaction whereby a carbon–carbon or carbon–heteroatom single bond is cleaved or undergoes lysis (breakdown) by hydrogen.Ralph Connor, Homer Adkins. Hydrogenolysis Of Oxygenated Organic Compounds. J. Am. Chem. Soc. ...

using

palladium on carbon Palladium on carbon, often referred to as Pd/C, is a form of palladium used as a catalyst. The metal is supported on activated carbon to maximize its surface area and activity. Uses Hydrogenation Palladium on carbon is used for catalytic hydrog ...

and hydrogen. The amino groups are then acetylated during the same step using

acetic anhydride Acetic anhydride, or ethanoic anhydride, is the chemical compound with the formula (CH3CO)2O. Commonly abbreviated Ac2O, it is the simplest isolable anhydride of a carboxylic acid and is widely used as a reagent in organic synthesis. It is a col ...

as the solvent. (4). Finally, compound 4 is reacted with

nitronium tetrafluoroborate Nitronium tetrafluoroborate is an inorganic compound with formula NO2BF4. It is a salt of nitronium cation and tetrafluoroborate anion. It is a colorless crystalline solid, which reacts with water to form the corrosive acids HF and HNO3. As suc ...

and

nitrosonium tetrafluoroborate Nitrosonium tetrafluoroborate, also called nitrosyl tetrafluoroborate, is a chemical compound with the chemical formula NOBF4. This colourless solid is used in organic synthesis as a nitrosating agent. NOBF4 is the nitrosonium salt of fluorobo ...

, resulting in HNIW.

Cocrystal product with HMX

In August 2012,

Onas Bolton The Selk'nam, also known as the Onawo or Ona people, are an indigenous people in the Patagonian region of southern Argentina and Chile, including the Tierra del Fuego islands. They were one of the last native groups in South America to be enc ...

et al. published results showing that a

cocrystal Cocrystals are "solids that are crystalline single phase materials composed of two or more different molecular or ionic compounds generally in a stoichiometric ratio which are neither solvates nor simple salts." A broader definition is that cocryst ...

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.

Cocrystal product with TNT

In August 2011,

Adam Matzger Adam J. Matzger, a researcher in polymers and crystals, is the Charles G. Overberger Collegiate Professor of Chemistry at the University of Michigan, and an associate editor for the American Chemical Society's journal '' Crystal Growth & Design'' ...

and

published results showing that a

of CL-20 and

TNT Trinitrotoluene (), more commonly known as TNT, more specifically 2,4,6-trinitrotoluene, and by its preferred IUPAC name 2-methyl-1,3,5-trinitrobenzene, is a chemical compound with the formula C6H2(NO2)3CH3. TNT is occasionally used as a reagen ...

had twice the stability of CL-20—safe enough to transport, but when heated to 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.

CL-20 covalent chains and networks

In 2017, K.P. Katin and M.M. Maslov designed one-dimensional covalent chains based on the CL-20 molecules. Such chains were constructed using CH₂ 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 CH₂ molecular bridges. It is shown that the use of CH₂ 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.

Synthesis

Cocrystal product with HMX

Cocrystal product with TNT

CL-20 covalent chains and networks

See also

References

Further reading