chemistry

Trimethylarsine

Trimethylarsine is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Trimethylarsine rather than just read about it. In short: Trimethylarsine (abbreviated TMA or TMAs) is the chemical compound with the formula (CH3)3As, commonly abbreviated AsMe3 or TMAs. This organic derivative of arsine has been used as a source of arsenic in microelectronics industry, a building block to other organoarsenic compounds, and serves as a ligand in coordination chemistry.

Key takeaways

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

Reference excerpt

Trimethylarsine (abbreviated TMA or TMAs) is the chemical compound with the formula (CH3)3As, commonly abbreviated AsMe3 or TMAs. This organic derivative of arsine has been used as a source of arsenic in microelectronics industry, a building block to other organoarsenic compounds, and serves as a ligand in coordination chemistry. It has a distinctive garlic-like smell. Trimethylarsine was discovered in 1854.

Structure and preparation AsMe3 is a pyramidal molecule. The As-C distances average 1.519 Å, and the C-As-C angles are 91.83° Trimethylarsine can be prepared by treatment of arsenic oxide with trimethylaluminium:

As2O3 + 1.5 [AlMe3]2 → 2 AsMe3 + 3/n (MeAl-O)n

Occurrence and reactions Trimethylarsine is the volatile byproduct of microbial action on inorganic forms of arsenic which are naturally occurring in rocks and soils at the parts-per-million level. Trimethylarsine has been reported only at trace levels (parts per billion) in landfill gas from Germany, Canada, and the U.S.A., and is the major arsenic-containing compound emitted by landfills. Trimethylarsine is pyrophoric due to the exothermic nature of the following reaction, which initiates combustion:

AsMe3 + 1/2 O2 → OAsMe3 (TMAO)

History Poisoning events due to a gas produced by certain microbes was assumed to be associated with the arsenic in paint. In 1893 the Italian physician Bartolomeo Gosio published his results on "Gosio gas" that was subsequently shown to contain trimethylarsine. Under wet conditions, the mold Microascus brevicaulis produces significant amounts of methyl arsines via methylation of arsenic-containing inorganic pigments, especially Paris green and Scheele's Green, which were once used in indoor wallpapers. Newer studies show that trimethylarsine has a low toxicity and could therefore not account for the death and the severe health problems observed in the 19th century.

Safety Trimethylarsine is potentially hazardous, although the toxicity of this compound is often exaggerated.

References

External links Index by Molecular Formula Information on Hazardous Chemicals by Class Microbial Methylation of Metalloids: Arsenic, Antimony, and Bismuth Arsenic Curiosa and Humanity

Illustrations

Worked examples

Example 1 — a first encounter with Trimethylarsine

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

In research: Trimethylarsine 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 Trimethylarsine 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: Trimethylarsine is common in secondary-school and first-year university syllabi. It links to neighbouring topics Foul-smelling chemicals, Methyl compounds, Organoarsenic compounds, so understanding it makes those chapters shorter.
In everyday life: Look for Trimethylarsine 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.

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How to study Trimethylarsine in 20 minutes

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

Frequently asked questions

What is Trimethylarsine in simple terms?

Why does Trimethylarsine 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 Trimethylarsine?

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 Trimethylarsine.