RDX

Key takeaways

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

Reference excerpt

RDX (Research Department Explosive or Royal Demolition Explosive), or hexogen, also known by other names, is an organic compound with the formula (CH2N2O2)3. It is white, odorless, tasteless, and widely used as an explosive. Chemically, it is classified as a nitroamine alongside HMX. It was used widely in World War II and remains common in military applications. It is lower performing and more toxic than modern replacements like TKX-50. RDX is often used in mixtures with other explosives and plasticizers or phlegmatizers (desensitizers); it is the explosive agent in C-4 plastic explosive and a key ingredient in Semtex. It is stable in storage and is considered one of the most energetic and brisant of the military high explosives, with a relative effectiveness factor of 1.60.

Name RDX is also less commonly known as cyclonite, hexogen (particularly in Russian, French and German-influenced languages), T4, and, chemically, as cyclotrimethylene trinitramine. In the 1930s, the Royal Arsenal, Woolwich, started investigating cyclonite to use against German U-boats that were being built with thicker hulls. The goal was to develop an explosive more energetic than TNT. For security reasons, Britain termed cyclonite "Research Department Explosive" (R.D.X.). The term RDX appeared in the United States in 1946. The first public reference in the United Kingdom to the name R.D.X. appeared in 1948; its authors were: the Managing Chemist, ROF Bridgwater; the Chemical Research and Development Department, Woolwich; and the Director of Royal Ordnance Factories, Explosives.

Usage

RDX was widely used during World War II, often in explosive mixtures with TNT such as Torpex, Composition B, Cyclotol, and H-6. RDX was used in one of the first plastic explosives. The bouncing bomb depth charges used in the "Dambusters Raid" each contained 6,600 pounds (3,000 kg) of Torpex. The Tallboy and Grand Slam bombs designed by Barnes Wallis also used Torpex. RDX is believed to have been used in many bomb plots, including terrorist plots. RDX is the base for a number of common military explosives:

Composition A: Granular explosive consisting of RDX and plasticizing wax, such as composition A-3 (91% RDX coated with 9% wax) and composition A-5 (98.5 to 99.1% RDX coated with 0.95 to 1.54% stearic acid). Composition B: Castable mixtures of 59.5% RDX and 39.4% TNT with 1% wax as desensitizer. Composition C: The original composition C was used in World War II, but there have been subsequent variations including C-2, C-3, and C-4. C-4 consists of RDX (91%); a plasticizer, dioctyl sebacate (5.3%); and a binder, which is usually polyisobutylene (2.1%); and a specially manufactured mineral oil (1.6%). Composition CH-6: 97.5% RDX, 1.5% calcium stearate, 0.5% polyisobutylene, and 0.5% graphite DBX (Depth Bomb Explosive): Castable mixture consisting of 21% RDX, 21% ammonium nitrate, 40% TNT, and 18% powdered aluminium, developed during World War II, it was to be used in underwater munitions as a substitute for Torpex employing only half the amount of then-scarce RDX, as the supply of RDX became more adequate, however, the mixture was shelved Cyclotol: Castable mixture of RDX (50–80%) with TNT (20–50%) designated by the amount of RDX/TNT, such as Cyclotol 70/30 HBX: Castable mixtures of RDX, TNT, powdered aluminium, and D-2 wax with calcium chloride H-6: Castable mixture of RDX, TNT, powdered aluminum, and paraffin wax (used as a phlegmatizing agent) PBX: RDX is also used as a major component of many polymer-bonded explosives (PBX); RDX-based PBXs typically consist of RDX and at least thirteen different polymer/co-polymer binders. Examples of RDX-based PBX formulations include, but are not limited to: PBX-9007, PBX-9010, PBX-9205, PBX-9407, PBX-9604, PBXN-106, PBXN-3, PBXN-6, PBXN-10, PBXN-201, PBX-0280, PBX Type I, PBXC-116, PBXAF-108, etc. Semtex (trade name): Plastic demolition explosive containing RDX and PETN as major energetic components Torpex: 42% RDX, 40% TNT, and 18% powdered aluminium; the mixture was designed during World War II and used mainly in underwater ordnance Outside military applications, RDX is also used in controlled demolition to raze structures. The demolition of the Jamestown Bridge in the U.S. state of Rhode Island was one instance where RDX shaped charges were used to remove the span.

Synthesis RDX is classified by chemists as a hexahydro-1,3,5-triazine derivative. In laboratory settings (industrial routes are described below separately) it is obtained by treating hexamine with white fuming nitric acid.

This nitrolysis reaction also produces methylene dinitrate, ammonium nitrate, and water as by-products. The overall reaction is:

C6H12N4 + 10 HNO3 → C3H6N6O6 + 3 CH2(ONO2)2 + NH4NO3 + 3 H2O Careful control of the acid mixture is necessary, as similar conditions produce a wide variety of partial deamination products. Indeed, the conventional cheap nitration agent, called "mixed acid", cannot be used for RDX synthesis because concentrated sulfuric acid used to stimulate the nitronium ion formation is too strong, decomposing hexamine into formaldehyde and ammonia. Modern syntheses employ hexahydro triacyl triazine, as it avoids formation of HMX.

History RDX was used by both sides in World War II. The US produced about 15,000 long tons (15,000 t) per month during WWII and Germany about 7,100 tonnes (7,000 long tons) per month. RDX had the major advantages of possessing greater explosive force than TNT and required no additional raw materials for its manufacture. Thus, it was also extensively used in World War II.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with RDX

Start with the simplest possible case. Write down what RDX 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 RDX 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 RDX 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 RDX

In research: RDX 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 RDX 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: RDX is common in secondary-school and first-year university syllabi. It links to neighbouring topics Convulsants, Explosive chemicals, GABAA receptor negative allosteric modulators, so understanding it makes those chapters shorter.
In everyday life: Look for RDX 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 RDX in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what RDX 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 RDX out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is RDX in simple terms?

RDX (Research Department Explosive or Royal Demolition Explosive), or hexogen, also known by other names, is an organic compound with the formula (CH2N2O2)3. It is white, odorless, tasteless, and widely used as an explosive.

Why does RDX 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 RDX?

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 RDX.