atsetüül

Atsetüül, also known as acetyl, is a two-carbon acyl substituent derived from acetic acid (ethanoic acid). It is the functional group -CO-CH3 that can be attached to various atoms (oxygen, nitrogen, sulfur) in a molecule, forming acetylated derivatives such as esters, amides, and thioesters. The group is often abbreviated Ac- in shorthand notation.

Chemically, the acetyl group is a carbonyl-containing fragment with formula CH3-CO-. It acts as an electron-withdrawing substituent, influencing reactivity, polarity and hydrolysis tendency of the compounds it resides in. Acetylation is the process of transferring the acetyl group to a substrate, typically using reagents such as acetyl chloride (CH3COCl) or acetic anhydride [(CH3CO)2O]. Reaction with alcohols yields acetate esters; reaction with amines yields amides; with thiols it forms thioesters. The reverse reaction, hydrolysis or deacetylation, can remove the group.

In biology, acetyl groups are central to metabolism and regulation. Acetyl-CoA carries acetyl groups into metabolic pathways, linking carbohydrate and lipid metabolism. Histone acetylation, catalyzed by histone acetyltransferases, modulates chromatin structure and gene expression. Protein N-terminal acetylation and various lysine acetylations are widespread post-translational modifications affecting stability and interactions.

Applications include pharmaceuticals and materials: acetylation modifies drug activity (for example aspirin is acetylated salicylic acid) and acetylated polymers such as acetyl cellulose are used in industry. Safety notes: reagents like acetyl chloride are corrosive and must be handled with appropriate precautions.