chemistry

Hydroacylation

Hydroacylation 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 Hydroacylation rather than just read about it. In short: Hydroacylation is a type of organic reaction in which an electron-rich unsaturated hydrocarbon inserts into a formyl C-H bond. With alkenes, the product is a ketone: RCHO + CH2=CHR' → RC(O)CH2CH2R' With an alkyne instead, the reaction produces an α,β-unsaturated ketone.

Key takeaways

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

Reference excerpt

Hydroacylation is a type of organic reaction in which an electron-rich unsaturated hydrocarbon inserts into a formyl C-H bond. With alkenes, the product is a ketone:

RCHO + CH2=CHR' → RC(O)CH2CH2R' With an alkyne instead, the reaction produces an α,β-unsaturated ketone. The reaction requires a metal catalyst or a radical initiator. Even so, the reaction is difficult to engineer, as oxidizing aldehydes to acyl radicals occurs only at high electrochemical potential. It is almost invariably practiced as an intramolecular reaction using homogeneous catalysts, often based on rhodium phosphines.

History Hydroacylation first appeared in 1949, part of Kharasch's studies on peroxide effects. Because chain transfer occurs very slowly, the radical reaction required a very large excess of aldehyde and, with dicarbonyl substrates, decarbonylation byproducts appeared in large quantity. In the 1970s, metal-catalyzed hydroacylation was discovered for the synthesis of certain prostanoids. The reaction required tin tetrachloride and a stoichiometric amount of Wilkinson's catalyst:

An equal amount of a cyclopropane was formed as the result of decarbonylation. The first catalytic application involved cyclization of 4-pentenal to cyclopentanone using (again) Wilkinson's catalyst. In this reaction the solvent was saturated with ethylene.

CH2=CHCH2CH2CHO → (CH2)4CO As of 2019, metal-catalyzed reactions continued to require rhodium catalysis. In the 1990s, studies on acyl radicals revealed that thiols or N-hydroxyphthalimide could catalyze rapid chain transfer, mostly removing the drawbacks of Kharasch's original radical reaction. However, substrate scope remained limited. Modern work focuses on photoredox catalysis, and has produced mediocre-yielding catalysts that handle arbitrary substrates.

Reaction mechanism In the presence of a metal catalyst, hydroacylation begins with two oxidative additions: of the alkene and into the aldehydic carbon-hydrogen bond. The relative order of these two coordinations is unclear. The product is an acyl-metal hydride alkene complex. Then the alkene ligand undergoes migratory insertion into either the metal-acyl or the metal-hydride bonds. Finally, the resulting alkyl-acyl or beta-ketoalkyl-hydride complex undergoes reductive elimination.

A competing side-reaction is decarbonylation of the intermediate acyl-metal hydride to give an alkane and a metal carbonyl:

R"C(O)-MLn-H → R"-M(CO)Ln-H → R"-H + M(CO)Ln

Asymmetric hydroacylation Hydroacylation as an asymmetric reaction was demonstrated in the form of a kinetic resolution. A true asymmetric synthesis was also described. Both conversions employed rhodium catalysts and a chiral diphosphine ligand. In one application the ligand is Me-DuPhos:

References

Illustrations

Worked examples

Example 1 — a first encounter with Hydroacylation

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

In research: Hydroacylation 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 Hydroacylation 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: Hydroacylation is common in secondary-school and first-year university syllabi. It links to neighbouring topics Organic reactions, so understanding it makes those chapters shorter.
In everyday life: Look for Hydroacylation 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 Hydroacylation in 20 minutes

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

Frequently asked questions

What is Hydroacylation in simple terms?

Hydroacylation is a type of organic reaction in which an electron-rich unsaturated hydrocarbon inserts into a formyl C-H bond. With alkenes, the product is a ketone: RCHO + CH2=CHR' → RC(O)CH2CH2R' With an alkyne instead, the reaction produces an α,β-unsaturated ketone.

Why does Hydroacylation 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 Hydroacylation?

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 Hydroacylation.