Nitromethane

Key takeaways

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

Reference excerpt

Nitromethane, sometimes shortened to simply "nitro", is an organic compound with the chemical formula CH3NO2. It is the simplest organic nitro compound. It is a polar liquid commonly used as a solvent in a variety of industrial applications such as in extractions, as a reaction medium, and as a cleaning solvent. As an intermediate in organic synthesis, it is used widely in the manufacture of pesticides, explosives, fibers, and coatings. Nitromethane is used as a fuel additive in various motorsports and hobbies, e.g. Top Fuel drag racing and miniature internal combustion engines in radio control, control line and free flight model aircraft.

Preparation Nitromethane is produced industrially by combining propane and nitric acid in the gas phase at 350–450 °C (662–842 °F). This exothermic reaction produces the four industrially significant nitroalkanes: nitromethane, nitroethane, 1-nitropropane, and 2-nitropropane. The reaction involves free radicals, including the alkoxyl radicals of the type CH3CH2CH2O, which arise via homolysis of the corresponding nitrite ester. These alkoxy radicals are susceptible to C—C fragmentation reactions, which explains the formation of a mixture of products.

Laboratory methods It can also be prepared by other methods that are of instructional value. The reaction of sodium chloroacetate with sodium nitrite in aqueous solution produces this compound, along with sodium chloride and sodium bicarbonate:

ClCH2COONa + NaNO2 + H2O → CH3NO2 + NaCl + NaHCO3

Uses The dominant use of the nitromethane is as a precursor reagent. A major derivative is chloropicrin (CCl3NO2), a widely used pesticide. It condenses with formaldehyde (Henry reaction) to eventually give tris(hydroxymethyl)aminomethane ("tris"), a widely used buffer and ingredient in alkyd resins.

Solvent and stabilizer The major application is as a stabilizer in chlorinated solvents. As an organic solvent, nitromethane has an unusual combination of properties: highly polar (εr = 36 at 20 °C and μ = 3.5 debye) but aprotic and weakly basic. This combination makes it useful for dissolving positively charged, strongly electrophilic species. It is a solvent for acrylate monomers, such as cyanoacrylates (more commonly known as "super-glues").

Fuel Although a minor application in terms of volume, nitromethane also is used as a fuel or fuel additive for sports and hobby. For some applications, it is mixed with methanol in racing cars, boats, and model engines. Nitromethane is used as a fuel in motor racing, particularly drag racing, as well as for radio-controlled model power boats, cars, planes and helicopters. In this context, nitromethane is commonly referred to as "nitro fuel" or simply "nitro", and is the principal ingredient for fuel used in the "Top Fuel" category of drag racing. The oxygen content of nitromethane enables it to burn with much less atmospheric oxygen than conventional fuels. During nitromethane combustion, nitric oxide (NO) is one of the major emission products along with CO2 and H2O. Nitric oxide contributes to air pollution, acid rain, and ozone layer depletion. Recent (2020) studies suggest the correct stoichiometric equation for the burning of nitromethane is:

4 CH3NO2 + 5 O2 → 4 CO2 + 6 H2O + 4 NO The amount of air required to burn 1 kg (2.2 lb) of gasoline is 14.7 kg (32 lb), but only 1.7 kg (3.7 lb) of air is required for 1 kg of nitromethane. Since an engine's cylinder can only contain a limited amount of air on each stroke, 8.6 times as much nitromethane as gasoline can be burned in one stroke. Nitromethane, however, has a lower specific energy: gasoline provides about 42–44 MJ/kg, whereas nitromethane provides only 11.3 MJ/kg. This analysis indicates that nitromethane generates about 2.3 times the power of gasoline when combined with a given amount of oxygen. Nitromethane can also be used as a monopropellant, i.e., a propellant that decomposes to release energy without added oxygen. It was first tested as rocket monopropellant in 1930s by Luigi Crocco from the Italian Rocket Society. There is a renewed interest in nitromethane as safer replacement of hydrazine monopropellant. The following equation describes this process:

2 CH3NO2 → 2 CO + 2 H2O + H2 + N2 Nitromethane has a laminar combustion velocity of approximately 0.5 m/s, somewhat higher than gasoline, thus making it suitable for high-speed engines. It also has a somewhat higher flame temperature of about 2,400 °C (4,350 °F). The high heat of vaporization of 0.56 MJ/kg together with the high fuel flow provides significant cooling of the incoming charge (about twice that of methanol), resulting in reasonably low temperatures. Nitromethane is usually used with rich air–fuel mixtures because it provides power even in the absence of atmospheric oxygen. When rich air–fuel mixtures are used, hydrogen and carbon monoxide are two of the combustion products. These gases often ignite, sometimes spectacularly, as the normally very rich mixtures of the still burning fuel exits the exhaust ports. Very rich mixtures are necessary to reduce the temperature of combustion chamber hot parts in order to control pre-ignition and subsequent detonation. Operational details depend on the particular mixture and engine characteristics. A small amount of hydrazine blended in nitromethane can increase the power output even further. With nitromethane, hydrazine forms an explosive salt that is again a monopropellant. This unstable mixture poses a severe safety hazard. The National Hot Rod Association and Academy of Model Aeronautics do not permit its use in competitions. In model aircraft and car glow fuel, the primary ingredient is generally methanol with some nitromethane (0% to 65%, but rarely over 30%, and 10–20% lubricants (usually castor oil and/or synthetic oil)). Even moderate amounts of nitromethane tend to increase the power created by the engine (as the limiting factor is often the air intake), making the engine easier to tune (adjust for the proper air/fuel ratio).

Former uses It formerly was used in the explosives industry as a component in a binary explosive formulation with ammonium nitrate and in shaped charges, and it was used as a chemical stabilizer to prevent decomposition of various halogenated hydrocarbons.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Nitromethane

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

In research: Nitromethane 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 Nitromethane 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: Nitromethane is common in secondary-school and first-year university syllabi. It links to neighbouring topics Drag racing, Explosive chemicals, Fuel additives, so understanding it makes those chapters shorter.
In everyday life: Look for Nitromethane 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 Nitromethane in 20 minutes

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

Frequently asked questions

What is Nitromethane in simple terms?

Nitromethane, sometimes shortened to simply "nitro", is an organic compound with the chemical formula CH3NO2. It is the simplest organic nitro compound.

Why does Nitromethane 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 Nitromethane?

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 Nitromethane.