chemistry

Pirkle's alcohol

Pirkle's alcohol 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 Pirkle's alcohol rather than just read about it. In short: Pirkle's alcohol is an off-white, crystalline solid that is stable at room temperature when protected from light and oxygen. This chiral molecule is typically used, in nonracemic form, as a chiral shift reagent in nuclear magnetic resonance spectroscopy, in order to simultaneously determine absolute configuration and enantiomeric purity of other chiral molecules.

Key takeaways

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

Reference excerpt

Pirkle's alcohol is an off-white, crystalline solid that is stable at room temperature when protected from light and oxygen. This chiral molecule is typically used, in nonracemic form, as a chiral shift reagent in nuclear magnetic resonance spectroscopy, in order to simultaneously determine absolute configuration and enantiomeric purity of other chiral molecules. The molecule is named after William H. Pirkle, Professor of Chemistry at the University of Illinois whose group reported its synthesis and its application as a chiral shift reagent.

Synthesis Pirkle's alcohol is synthesized by trifluoroacetylation of anthracene, to yield trifluoromethyl 9-anthryl ketone. Trifluoromethyl 9-anthryl ketone may be reduced with a chiral hydride reagent prepared from lithium aluminium hydride and (4S,5S)-(–)-2-ethyl-4-hydroxymethyl-5-phenyl-2-oxazoline to generate Pirkle's alcohol with R absolute configuration. Alternatively, trifluoromethyl 9-anthryl ketone may be reduced with sodium borohydride to generate racemic Pirkle's alcohol. The enantiomers are then derivatized to diastereomeric carbamates using enantioenriched 1-(1-Naphthyl)ethyl isocyanate (also developed by Pirkle). These diastereomers may be separated by column chromatography and hydrolyzed to obtain each enantiomer of Pirkle's alcohol in enantiopure form.

Application The determination of enantiomeric purity and absolute configuration is frequently necessary in organic synthesis. Pirkle's alcohol is applied to obtain this information by NMR spectroscopy. When Pirkle's alcohol is in solution with an ensemble of chiral molecules, short-lived diastereomeric solvates may be formed from Pirkle's alcohol and the enantiomers of the analyte. Enantiomorphic protons of the analyte enantiomers, which without Pirkle's alcohol are indistinguishable by NMR, become diastereomorphic when the analyte interacts with Pirkle's alcohol, and appear as different signals in an NMR spectrum. The relative magnitude of the signals quantitatively reveals the enantiomeric purity of the analyte. Also, a model of the solvated complex may be used to deduce absolute configuration of an enantioenriched analyte.

See also 2,2,2-Trifluoroethanol Mosher's acid 9-Anthracenemethanol

References

Illustrations

Worked examples

Example 1 — a first encounter with Pirkle's alcohol

Start with the simplest possible case. Write down what Pirkle's alcohol 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 Pirkle's alcohol 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 Pirkle's alcohol 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 Pirkle's alcohol

In research: Pirkle's alcohol 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 Pirkle's alcohol 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: Pirkle's alcohol is common in secondary-school and first-year university syllabi. It links to neighbouring topics Anthracenes, Secondary alcohols, Stereochemistry, so understanding it makes those chapters shorter.
In everyday life: Look for Pirkle's alcohol 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 Pirkle's alcohol in 20 minutes

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

Frequently asked questions

What is Pirkle's alcohol in simple terms?

Why does Pirkle's alcohol 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 Pirkle's alcohol?

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 Pirkle's alcohol.