chemistry

Rearrangement reaction

Rearrangement reaction 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 Rearrangement reaction rather than just read about it. In short: In organic chemistry, a rearrangement reaction is a broad class of organic reactions "that involves a change of connectivity". Usually the term rearrangement refers to intramolecular processes involving modification of carbon skeleton.

Key takeaways

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

Reference excerpt

In organic chemistry, a rearrangement reaction is a broad class of organic reactions "that involves a change of connectivity". Usually the term rearrangement refers to intramolecular processes involving modification of carbon skeleton. Often a substituent moves from one atom to another atom in the same molecule, hence these reactions are usually intramolecular. In the example below, the substituent R moves from carbon atom 1 to carbon atom 2:

− C | R − C − C − ⟶ − C − C | R − C − {\displaystyle {-}{\underset {| \atop \displaystyle \color {Blue}{\ce {R}}}{{\ce {C}}}}{\ce {-C-C{-}-> {-C-}}}{\underset {| \atop \displaystyle \color {Blue}{\ce {R}}}{{\ce {C}}}}{\ce {-C}}{-}}

A rearrangement is not well represented by simple and discrete electron transfers (represented by curved arrows in organic chemistry texts). The actual mechanism of alkyl groups moving, as in Wagner–Meerwein rearrangement, probably involves transfer of the moving alkyl group fluidly along a bond, not ionic bond-breaking and forming. In pericyclic reactions, explanation by orbital interactions give a better picture than simple discrete electron transfers. It is, nevertheless, possible to draw the curved arrows for a sequence of discrete electron transfers that give the same result as a rearrangement reaction, although these are not necessarily realistic. In allylic rearrangement, the reaction is indeed ionic.

1,2-rearrangements

A 1,2-rearrangement is an organic reaction where a substituent moves from one atom to another atom in a chemical compound. In a 1,2 shift the movement involves two adjacent atoms but moves over larger distances are possible. Skeletal isomerization is not normally encountered in the laboratory, but is the basis of large applications in oil refineries. In general, straight-chain alkanes are converted to branched isomers by heating in the presence of a catalyst. Examples include isomerisation of n-butane to isobutane and pentane to isopentane. Highly branched alkanes have favorable combustion characteristics for internal combustion engines.

Further examples are the Wagner–Meerwein rearrangement:

and the Beckmann rearrangement, which is relevant to the production of certain nylons:

Pericyclic reactions

A pericyclic reaction is a type of reaction with multiple carbon–carbon bond making and breaking wherein the transition state of the molecule has a cyclic geometry, and the reaction progresses in a concerted fashion. Examples are hydride shifts

and the Claisen rearrangement:

Other rearrangement reactions

1,3-rearrangements 1,3-rearrangements take place over 3 carbon atoms. Examples:

the Fries rearrangement a 1,3-alkyl shift of verbenone to chrysanthenone

See also Amadori rearrangement Curtius rearrangement Hofmann rearrangement Lossen rearrangement Mumm rearrangement Photochemical rearrangement Pinacol rearrangement Schmidt reaction Thermal rearrangement of aromatic hydrocarbons Tiemann rearrangement Wolff rearrangement

References

Illustrations

Worked examples

Example 1 — a first encounter with Rearrangement reaction

Start with the simplest possible case. Write down what Rearrangement reaction 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 Rearrangement reaction 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 Rearrangement reaction 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 Rearrangement reaction

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

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

Frequently asked questions

What is Rearrangement reaction in simple terms?

Why does Rearrangement reaction 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 Rearrangement reaction?

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 Rearrangement reaction.