chemistry

Methaneseleninic acid

Methaneseleninic acid 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 Methaneseleninic acid rather than just read about it. In short: Methaneseleninic acid (methylseleninic acid or MSA) is an organoselenium compound, a seleninic acid with the chemical formula CH3SeO2H. Its structure is CH3−Se(=O)−OH.

Key takeaways

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

Reference excerpt

Methaneseleninic acid (methylseleninic acid or MSA) is an organoselenium compound, a seleninic acid with the chemical formula CH3SeO2H. Its structure is CH3−Se(=O)−OH.

Preparation Methaneseleninic acid is conveniently synthesized through oxidation of commercially available dimethyl diselenide by 3% hydrogen peroxide.

CH3−Se−Se−CH3 + H2O2 → 2 CH3−Se(=O)−OH Seleninic acids can be prepared by oxidation of selenoesters with one equivalent of dimethyldioxirane (DMDO). Use of excess DMDO affords little studied selenonic acids (R−Se(=O)2−OH).

R−Se−C(=O)−R' + DMDO → R−Se(=O)−OH R−Se−C(=O)−R' + excess DMDO → R−Se(=O)2−OH Selenenic acids, formed during the syn-elimination of selenoxides, undergo spontaneous disproportionation into the corresponding seleninic acids and diselenides:

4 R−Se−OH → 2 R−Se(=O)−OH + R−Se−Se−R

Structure and properties Methaneseleninic acid, from decomposition of Se-methylselenocysteine Se-oxide but also available commercially, has been characterized by X-ray crystallography. The configuration about the selenium atom is pyramidal, with Se-C = 1.925(8) Å, Se-O = 1.672(7) Å, Se-OH = 1.756(7) Å, the angle OSeO = 103.0(3)°, the angle HO-Se-C = 93.5(3)°, and the angle OSeC = 101.4(3)°. The structure is isomorphous to that of methanesulfinic acid Optical isomers of methaneseleninic acid can be isolated as chiral crystals by recrystallization from a mixture of methanol and toluene. The absolute configuration of one of the enantiomers was determined by X-ray crystallography. Optically active methaneseleninic acid was stable toward racemization in the solid state, although it racemized very rapidly in solution.

Anticancer activity Methaneseleninic acid shows potential anticancer activity and is a model for studying the anticancer effects of selenium in vitro. Methaneseleninic acid shows superior in vivo inhibitory efficacy toward human prostate cancer compared to selenomethionine or selenite (ion). It has recently been reported that methaneseleninic acid enhances the efficacy of paclitaxel for treatment of triple-negative breast cancer, that methaneseleninic acid functions as an aromatase inhibitor, of possible use in therapy for estrogen receptor-positive breast cancer in postmenopausal women, that methaneseleninic acid shows promise as a sensitizing agent for apoptosis induced by the Bcl-2-family inhibitor ABT-737 in several cancer lines, and that methaneseleninic acid restricts tumor growth in the nude mouse model of metastatic breast cancer and Lewis lung carcinoma in mice. Methaneselenol (CH3SeH) can be produced in vivo by reduction of methaneseleninic acid and may in fact be the key metabolite responsible for selenium's anticancer activity through generation of superoxide. The reduction of methaneseleninic acid by mammalian thioredoxin reductase has been studied.

References

Illustrations

Worked examples

Example 1 — a first encounter with Methaneseleninic acid

Start with the simplest possible case. Write down what Methaneseleninic acid 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 Methaneseleninic acid 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 Methaneseleninic acid 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 Methaneseleninic acid

In research: Methaneseleninic acid 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 Methaneseleninic acid 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: Methaneseleninic acid is common in secondary-school and first-year university syllabi. It links to neighbouring topics Organic acids, Organic compounds with 1 carbon atom, Organoselenium compounds, so understanding it makes those chapters shorter.
In everyday life: Look for Methaneseleninic acid 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 Methaneseleninic acid in 20 minutes

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

Frequently asked questions

What is Methaneseleninic acid in simple terms?

Methaneseleninic acid (methylseleninic acid or MSA) is an organoselenium compound, a seleninic acid with the chemical formula CH3SeO2H. Its structure is CH3−Se(=O)−OH.

Why does Methaneseleninic acid 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 Methaneseleninic acid?

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 Methaneseleninic acid.