Acyl

An acyl group is a functional group derived from an organic acid by removal of a hydroxyl group (−OH) from all acid groups. It is commonly represented as RCO−, where R represents an alkyl group or an aryl group. Acyl groups are key intermediates in organic chemistry and are involved in a variety of chemical reactions, including acylation and esterification.

Structure and Nomenclature

The general structure of an acyl group is R−C(=O)−, where R can be any organic substituent. The carbon atom is double-bonded to an oxygen atom, forming a carbonyl group, and is single-bonded to the R group. The simplest acyl group is the formyl group (HCO−), derived from formic acid.

Acyl groups are named by replacing the "-ic acid" suffix of the parent acid with "-yl". For example, the acyl group derived from acetic acid is called the acetyl group (CH₃CO−).

Reactivity

Acyl groups are highly reactive due to the presence of the carbonyl group, which is polarized with a partial positive charge on the carbon atom. This makes acyl groups susceptible to nucleophilic attack, a key step in many organic reactions.

Acylation Reactions

Acylation is the process of adding an acyl group to a compound. This can occur through various mechanisms, such as the Friedel-Crafts acylation, where an acyl chloride reacts with an aromatic ring in the presence of a Lewis acid catalyst.

Esterification

Acyl groups can react with alcohols to form esters, a process known as esterification. This reaction is typically catalyzed by acids and involves the nucleophilic attack of the alcohol on the carbonyl carbon of the acyl group.

Biological Importance

In biochemistry, acyl groups are important in the formation of lipids, such as triglycerides and phospholipids. They are also involved in the modification of proteins through acylation, which can affect protein function and localization.

Also see

• Carbonyl group
• Carboxylic acid
• Ester
• Amide
• Friedel-Crafts reaction