What does acyl mean?
In chemistry, an acyl is a univalent radical with the general formula RCO–, formed when the hydroxyl group (–OH) is removed from an oxoacid such as a carboxylic acid. The carbonyl carbon at its centre bonds to an organic group R on one side and remains available to attach to another atom or molecule on the other, which makes acyl groups central to many reactions in organic chemistry and biochemistry. They appear constantly in discussions of fats, proteins, and metabolic pathways: fatty acids are shuttled between enzymes as acyl groups bound to coenzyme A, and acyl carrier proteins ferry growing chains during lipid synthesis. Common derivatives include acyl chlorides, widely used reagents for introducing acyl groups into other molecules. The term belongs firmly to technical and academic registers — students meet it in organic chemistry courses, and researchers use it daily — but it is essentially unknown in everyday speech. Its importance lies less in the word itself than in what it names: one of the most versatile and ubiquitous building blocks in molecular science.
nounIn chemistry, a univalent organic radical derived from an oxoacid by removal of the hydroxyl group, having the general formula RCO–.
- A univalent radical of general formula RCO– derived from an oxoacid by removal of the hydroxyl group, especially in organic chemistry.
"The enzyme transfers an acyl group onto the glycerol backbone during lipid synthesis."
"Fatty acids are activated by attachment to coenzyme A before their acyl groups are transferred in metabolism."
"Acylation reactions introduce an acyl group into a molecule, often using an acyl chloride as the reagent."
Used when referring to multiple acyl radicals or to different acyl substituents within a compound or mixture.
"The membrane contains a mixture of phospholipids with saturated and unsaturated acyls attached to the glycerol backbone."
The word 'acyl' was stitched together in the 1830s from 'acetyl' and 'oxy' — chemists literally invented it to name a fragment they could never isolate on its own.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of acyl
The term 'acyl' was coined in German in the early nineteenth century, around the 1830s, by the chemists Justus von Liebig and Friedrich Wöhler, who combined elements of 'acetyl' and 'oxy' to name the radical common to organic acids. It entered English scientific usage shortly afterwards as organic chemistry developed its systematic nomenclature. Related terms sharing this root include 'acetic', 'acetate', and 'acetyl', all tracing back ultimately to Latin 'acetum', meaning vinegar.
Related word forms
How acyl is actually used
Strictly technical vocabulary used almost exclusively in chemistry, biochemistry, and related scientific writing; rarely encountered outside academic or laboratory contexts.
Easily confused with acyl
An alkyl is a radical derived from an alkane by loss of a hydrogen atom and contains only carbon and hydrogen, whereas an acyl contains a carbonyl carbon double-bonded to oxygen.