What are Tautomers? Definition, Examples, and Significance in Organic Chemistry

A tautomer is a molecule that can exist in two or more different forms, called tautomers, which are interconvertible through a chemical reaction that does not involve the addition or removal of atoms. Tautomers are isomers, meaning they have the same molecular formula but differ in their arrangement of atoms.

Tautomers are often found in organic chemistry, where a molecule can exist in both a keto (carbonyl) and an enol (enol) form. The keto form has a carbonyl group (-COH), while the enol form has a hydroxyl group (-OH) attached to the carbon atom that is double-bonded to the oxygen atom. These two forms are tautomers because they can interconvert through a shift of the double bond between the carbon and oxygen atoms.

For example, the molecule acetone (CH3COCH3) exists in both keto and enol forms:

Keto form: CH3COCH3
Enol form: CH3C(OH)CH3

These two forms are tautomers because they can interconvert through a shift of the double bond between the carbon and oxygen atoms. The keto form is more stable under basic conditions, while the enol form is more stable under acidic conditions.

Tautomers play an important role in organic chemistry, as they can affect the physical and chemical properties of a molecule. For example, the tautomerism of acetone can affect its solubility, reactivity, and stability. Understanding tautomers is essential for designing and optimizing organic reactions, as well as for understanding the properties and behavior of organic compounds.