science

Hexamethylphosphoramide

Hexamethylphosphoramide is a science 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 Hexamethylphosphoramide rather than just read about it. In short: Hexamethylphosphoramide, often abbreviated HMPA, is a phosphoramide (an amide of phosphoric acid) with the formula [(CH3)2N]3PO. This colorless liquid is used as a solvent in organic synthesis.

Key takeaways

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

Reference excerpt

Hexamethylphosphoramide, often abbreviated HMPA, is a phosphoramide (an amide of phosphoric acid) with the formula [(CH3)2N]3PO. This colorless liquid is used as a solvent in organic synthesis.

Structure and reactivity HMPA is the oxide of tris(dimethylamino)phosphine, P(NMe2)3. Like other phosphine oxides (such as triphenylphosphine oxide), the molecule has a tetrahedral core and a P=O bond that is highly polarized, with significant negative charge residing on the oxygen atom. Compounds containing a nitrogen–phosphorus bond typically are degraded by hydrochloric acid to form a protonated amine and phosphate. It dissolves alkali metal salts and alkali metals, forming blue solutions which are stable for a few hours. Solvated electrons are present in these blue solutions.

Applications HMPA is a specialty solvent for polymers, gases, and organometallic compounds. It improves the selectivity of lithiation reactions by breaking up the oligomers of lithium bases such as butyllithium. Because HMPA selectively solvates cations, it accelerates otherwise slow SN2 reactions by generating more bare anions. The basic nitrogen centers in HMPA coordinate strongly to Li+. HMPA is a ligand in the useful reagents based on molybdenum peroxide complexes, for example, MoO(O2)2(HMPA)(H2O) is used as an oxidant in organic synthesis.

Alternative reagents Dimethyl sulfoxide can often be used in place of HMPA as a cosolvent. Both are strong hydrogen bond acceptors, and their oxygen atoms bind metal cations. Other alternatives to HMPA include the N,N′-tetraalkylureas DMPU (dimethylpropyleneurea) or DMI (1,3-dimethyl-2-imidazolidinone). Tripyrrolidinophosphoric acid triamide (TPPA) has been reported to be a good substitute reagent for HMPA in reductions with samarium diiodide and as a Lewis base additive to many reactions involving samarium ketyls.

Toxicity HMPA is only mildly toxic but has been shown to cause cancer in rats. HMPA can be degraded by the action of hydrochloric acid.

References

External links "Hexamethylphosphoramide CAS No. 680-31-9" (PDF). Report on Carcinogens (12th ed.). National Toxicology Program, Department of Health and Human Services. 2011. "Hexamethyl phosphoramide". NIOSH Pocket Guide to Chemical Hazards. Centers for Disease Control and Prevention, Department of Health and Human Services. 2011. Merck Index. Vol. 4761 (12th ed.).

Illustrations

Worked examples

Example 1 — a first encounter with Hexamethylphosphoramide

Start with the simplest possible case. Write down what Hexamethylphosphoramide claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, 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 Hexamethylphosphoramide 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 Hexamethylphosphoramide 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 Hexamethylphosphoramide

In research: Hexamethylphosphoramide appears in science 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 Hexamethylphosphoramide 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: Hexamethylphosphoramide is common in secondary-school and first-year university syllabi. It links to neighbouring topics IARC Group 2B carcinogens, Phosphoramides, Solvents, so understanding it makes those chapters shorter.
In everyday life: Look for Hexamethylphosphoramide 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 Hexamethylphosphoramide in 20 minutes

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

Frequently asked questions

What is Hexamethylphosphoramide in simple terms?

Hexamethylphosphoramide, often abbreviated HMPA, is a phosphoramide (an amide of phosphoric acid) with the formula [(CH3)2N]3PO. This colorless liquid is used as a solvent in organic synthesis.

Why does Hexamethylphosphoramide matter?

Because it connects several science 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 Hexamethylphosphoramide?

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 Hexamethylphosphoramide.