What is a protecting group and provide an example.

A protecting group is a chemical modification used to temporarily mask a reactive functional group.

Protecting groups are commonly used in organic synthesis to protect a functional group that may react with a reagent or catalyst during a reaction. By temporarily masking the reactive group, the reaction can be carried out selectively on another part of the molecule. Once the reaction is complete, the protecting group can be removed to reveal the original functional group.

For example, in peptide synthesis, the amino group (-NH2) of an amino acid is often protected with a group such as the t-butoxycarbonyl (Boc) group. This protects the amino group from reacting with other reagents during the synthesis, allowing the peptide bond to be formed selectively between the carboxylic acid and the unprotected amino group of another amino acid. Once the peptide bond is formed, the Boc group can be removed with an acid to reveal the original amino group.

Protecting groups are also used in the synthesis of natural products, pharmaceuticals, and other complex organic molecules. The choice of protecting group depends on the specific functional group being protected and the reaction conditions. Common protecting groups include acetyl (Ac), benzyl (Bn), and methyl (Me) groups.