Pinacol Pinacolone Rearrangement

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Pinacol and pinacolone rearrangement was first described by Wilhelm Rudolph Fittig. Although Fittig wrongly assumed the molecular formula of acetone as (C3H3O)n. Then Aleksandr Butlerov correctly identified the reation products.

What is Pinacol and Pinacolone?

As the name suggests pinacol contains alcohol functional group while pinacolone contains ketone functional group. Pinacol is a compound which has two hydroxyl groups each attached to an adjacent carbon atom. IUPAC name of pinacol is 2,3-Dimethylbutane-2,3-diol. Pinacol structure is given below – 

Pinacolone is an organic compound containing ketone functional group. It is a colourless liquid and has an odor of peppermint or camphor. IUPAC name of pinacolone is 3,3-Dimethyl-2-butanone. Pinacolone structure is given below – 

Pinacol Pinacolone Rearrangement Reaction 

Conversion of an alcohol having two adjacent alcohol groups (pinacol) to a ketone (pinacolone) by the action of an acid (catalyst) is known as pinacol pinacolone rearrangement reaction. 

Pinacol Pinacolone Rearrangement Reaction Mechanism 

Pinacol Pinacolone rearrangement reaction mechanism can be explained by following four steps which takes place in the reaction- 

Step 1. Protonation of a hydroxyl group 

In this step proton or hydrogen ion coming from acid (H2SO4 breaks into H+ and HSO4-ions) gets attached to hydroxide group of pinacol. Reaction is given below – 

Step 2. Loss of water molecule 

In this step water molecule gets detached from the compound and gives carbocation. Reaction is given below-

Step 3. Methyl migration 

In this step methyl group migrated from one carbon to another carbon atom. It gets attached to positively charged carbon atom of carbocation. Reaction is given below – 

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Step 4. Deprotonation 

In this step proton which got attached to pinacol in 1st step gets detached as this proton was generated by acid catalyst during the reaction. When proton gets detached from carbocation, final product pinacolone is formed. Reaction is given as follows – 

Applications of Pinacolone (Product of Pinacol Rearrangement)

Pinacolone is a colourless liquid which has the chemical formula C6H12O. It is the product of pinacol pinacolone rearrangement reaction. It is very useful in production of fungicides, herbicides, pesticides and pharmaceuticals. Few uses of pinacolone are as follows - 

  • Pinacolone is used in the analysis of vibunazole. 

  • It is used in the synthesis of pinacidil and naminidil.

  • It is used in fungicides, herbicides and pesticides. 

  • It is used in the production of triadimefon, paclobutrazol, uniconazole and metribuzin. 

  • It is useful in production of pharmaceuticals. 

If you are looking for more name reactions, then you can go through the article ‘Important chemical reactions for Class 12 Chemistry’ available on Vedantu website. You can register yourself on Vedantu and download Vedantu app to get free PDFs of NCERT Solutions, revision notes, study material and mock tests.