HMX

Key takeaways

HMX belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect HMX to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HMX from memory before moving on to harder problems.

Reference excerpt

HMX, also called octogen, is a powerful and relatively insensitive nitroamine high explosive chemically related to RDX. The compound's name is the subject of much speculation, having been variously listed as High Melting Explosive, High-velocity Military Explosive, or High-Molecular-weight RDX, as well as Her Majesty's Explosive. The molecular structure of HMX consists of an eight-membered ring of alternating carbon and nitrogen atoms, with a nitro group attached to each nitrogen atom. Because of its high mass-specific enthalpy of formation, it is one of the most potent chemical explosives manufactured, although a number of newer ones, including HNIW, TKX-50, and ONC, are more powerful.

Synthesis HMX is more complicated to manufacture than most explosives, and this confines it to specialist applications. It and RDX are both produced by the Bachmann process—nitration of hexamine using a mixture of ammonium nitrate and nitric acid in a mixture of acetic acid and acetic anhydride as solvent—with the major product determined by the specific reaction conditions.

Applications Also known as cyclotetramethylene-tetranitramine, tetrahexamine tetranitramine, or octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine, HMX was first made in 1930. In 1949 it was discovered that HMX can be prepared by nitrolysis of RDX. Nitrolysis of RDX is performed by dissolving RDX in a 55% HNO3 solution, followed by placing the solution on a steambath for about six hours. HMX is used almost exclusively in military applications, including as the detonator in nuclear weapons, in the form of polymer-bonded explosive, and as a solid-rocket propellant. HMX is used in melt-castable explosives when mixed with TNT, which as a class are referred to as "octols". Additionally, polymer-bonded explosive compositions containing HMX are used in the manufacture of missile warheads and armor-piercing shaped charges. HMX is also used in the process of perforating the steel casing in oil and gas wells. The HMX is built into a shaped charge that is detonated within the wellbore to punch a hole through the steel casing and surrounding cement out into the hydrocarbon-bearing formations. The pathway that is created allows formation fluids to flow into the wellbore and onward to the surface. The Hayabusa2 space probe used HMX to excavate a hole in an asteroid in order to access material that had not been exposed to the solar wind. Ongoing research aims to reduce its sensitivity and improve some manufacturing properties.

Health and environmental fate

Analytical methods HMX enters the environment through air, water, and soil because it is widely used in military and civil applications. At present, reverse-phase HPLC and more sensitive LC-MS methods have been developed to accurately quantify the concentration of HMX in a variety of matrices in environmental assessments.

Toxicity At present, the information needed to determine if HMX causes cancer is insufficient. Due to the lack of information, EPA has determined that HMX is not classifiable as to its human carcinogenicity. The available data on the effects on human health of exposure to HMX are limited. HMX causes CNS effects similar to those of RDX, but at considerably higher doses. In one study, volunteers submitted to patch testing, which produced skin irritation. Another study of a cohort of 93 workers at an ammunition plant found no hematological, hepatic, autoimmune, or renal diseases. However, the study did not quantify the levels of exposure to HMX. HMX exposure has been investigated in several studies on animals. Overall, the toxicity appears to be quite low. HMX is poorly absorbed by ingestion. When applied to the dermis, it induces mild skin irritation but not delayed contact sensitization. Various acute and subchronic neurobehavioral effects have been reported in rabbits and rodents, including ataxia, sedation, hyperkinesia, and convulsions. The chronic effects of HMX that have been documented through animal studies include decreased hemoglobin, increased serum alkaline phosphatase, and decreased albumin. Pathological changes were also observed in the animals' livers and kidneys. Gas exchange rate was used as an indicator of chemical stress in Northern bobwhite quail (Colinus virginianus) eggs, and no evidence of alterations in metabolic rates associated with HMX exposure was observed. No data are available concerning the possible reproductive, developmental, or carcinogenic effects of HMX. HMX is considered less toxic than TNT or RDX. Remediating HMX-contaminated water supplies has proven to be successful.

Biodegradation Both wild and transgenic plants can phytoremediate explosives from soil and water.

See also 2,4,6-Tris(trinitromethyl)-1,3,5-triazine 4,4'-Dinitro-3,3'-diazenofuroxan (DDF) Heptanitrocubane (HNC) HHTDD Octanitrocubane (ONC) RE factor

Notes

References Cooper, Paul W. (1996). Explosives Engineering. New York: Wiley-VCH. ISBN 978-0-471-18636-6. OCLC 34409473. Retrieved 9 June 2014. Urbanski, Tadeusz (1967). Chemistry and Technology of Explosives. Vol. III. Warszawa: Polish Scientific Publishers.

Further reading Schmidt, Eckart W. (2022). "1,3,5,7-Tetranitro-1,3,5,7-tetraazacyclooctane, Octogen (HMX)". Nitramines. Encyclopedia of Liquid Fuels. De Gruyter. pp. 4327–4371. doi:10.1515/9783110750287-035. ISBN 978-3-11-075028-7.

Illustrations

Worked examples

Example 1 — a first encounter with HMX

Start with the simplest possible case. Write down what HMX claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to HMX before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about HMX ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of HMX

In research: HMX appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses HMX in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: HMX is common in secondary-school and first-year university syllabi. It links to neighbouring topics Eight-membered rings, Explosive chemicals, Nitroamines, so understanding it makes those chapters shorter.
In everyday life: Look for HMX outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study HMX in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HMX means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain HMX out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HMX in simple terms?

HMX, also called octogen, is a powerful and relatively insensitive nitroamine high explosive chemically related to RDX. The compound's name is the subject of much speculation, having been variously listed as High Melting Explosive, High-velocity Military Explosive, or High-Molecular-weight RDX, as…

Why does HMX matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study HMX?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on HMX.