In organic chemistry, acetyl is a functional group with the chemical formula −COCH3 and the structure −C(=O)−CH3. It is sometimes represented by the symbol Ac[5][6] (not to be confused with the element actinium). In IUPAC nomenclature, acetyl is called ethanoyl.
 | |
| Names | |
|---|---|
| IUPAC name | |
| Systematic IUPAC name Methyloxidocarbon(•)[4] (additive) | |
| Identifiers | |
3D model (JSmol) | |
| Abbreviations | Ac |
| 1697938 | |
| ChEBI | |
| ChemSpider | |
| 786 | |
PubChem CID | |
| |
| |
| Properties | |
| C2H3O | |
| Molar mass | 43.045 g·mol−1 |
| Thermochemistry | |
Std enthalpy of formation (ΔfH⦵298) | −15 to −9 kJ mol−1 |
| Related compounds | |
Related compounds | Acetone Carbon monoxide Acetic acid |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
The acetyl group contains a methyl group (−CH3) single-bonded to a carbonyl (C=O), making it an acyl group. The carbonyl center of an acyl radical has one nonbonded electron with which it forms a chemical bond to the remainder R of the molecule.
The acetyl moiety is a component of many organic compounds, including acetic acid, the neurotransmitter acetylcholine, acetyl-CoA, acetylcysteine, acetaminophen (also known as paracetamol), and acetylsalicylic acid (also known as aspirin).
Acetylation
In nature
The introduction of an acetyl group into a molecule is called acetylation. In biological organisms, acetyl groups are commonly transferred from acetyl-CoA to other organic molecules. Acetyl-CoA is an intermediate both in the biological synthesis and in the breakdown of many organic molecules. Acetyl-CoA is also created during the second stage of cellular respiration, pyruvate decarboxylation, by the action of pyruvate dehydrogenase on pyruvic acid.[7]
Histones and other proteins are often modified by acetylation. For example, on the DNA level, histone acetylation by acetyltransferases (HATs) causes an expansion of chromatin architecture, allowing for genetic transcription to occur. However, removal of the acetyl group by histone deacetylases (HDACs) condenses DNA structure, thereby preventing transcription.[8]
Synthetic organic and pharmaceutical chemistry
Acetylation can be achieved using a variety of methods, most commonly with the use of acetic anhydride or acetyl chloride, often in the presence of a tertiary or aromatic amine base. A typical acetylation is the conversion of glycine to N-acetylglycine:[9]
Pharmacology
Acetylated organic molecules exhibit increased ability to cross the selectively permeable blood–brain barrier.[citation needed] Acetylation helps a given drug reach the brain more quickly, making the drug's effects more intense and increasing the effectiveness of a given dose.[citation needed] The acetyl group in acetylsalicylic acid (aspirin) enhances its effectiveness relative to the natural anti-inflammatant salicylic acid. In similar manner, acetylation converts the natural painkiller morphine into the far more potent heroin (diacetylmorphine).
There is some evidence that acetyl-L-carnitine may be more effective for some applications than L-carnitine.[10] Acetylation of resveratrol holds promise as one of the first anti-radiation medicines for human populations.[11]
Etymology
The term was coined by Justus von Liebig in 1839 to denote what he believed to be the radical of the acetic acid, and what we now call the vinyl group (coined in 1851). When it became a scientific consensus that his theory was wrong and the acid had a different radical, the name was carried over to the correct one, but the name of acetylene (coined in 1860) was retained.[12]
See also
- Acetaldehyde
- Acetoxy group
- Histone acetylation and deacetylation
- Polyoxymethylene plastic, a.k.a. acetal resin, a thermoplastic