# Acetyl group

Names Identifiers IUPAC name Acetyl (preferred to ethanoyl)[1][2][3] Systematic IUPAC name Methyloxidocarbon(•)[4] (additive) CAS Number .mw-parser-output .plainlist ol,.mw-parser-output .plainlist ul{line-height:inherit;list-style:none;margin:0;padding:0}.mw-parser-output .plainlist ol li,.mw-parser-output .plainlist ul li{margin-bottom:0}3170-69-2 3D model (JSmol) Interactive image Abbreviations Ac Beilstein Reference 1697938 ChEBI CHEBI:46887 ChemSpider 121499 Gmelin Reference 786 PubChem CID 137849 InChI InChI=1S/C2H3O/c1-2-3/h1H3 Key: TUCNEACPLKLKNU-UHFFFAOYSA-N SMILES C[C]=O Chemical formula C2H3O Molar mass 43.045 g·mol−1 Std enthalpy offormation (ΔfH⦵298) −15 to −9 kJ mol−1 Related compounds Acetone Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

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] (not to be confused with the element actinium). In IUPAC nomenclature, acetyl is called ethanoyl, although this term is barely heard.[citation needed]

The acetyl group contains a methyl group (−CH3) single-bonded to a carbonyl (C=O). 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 synthetase 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.

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.[6]

### Synthetic organic and pharmaceutical chemistry

Acetylation can be achieved using a variety of methods, the most common one being via 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:[7]

${\displaystyle {\ce {H2NCH2CO2H + (CH3CO)2O -> CH3C(O)NHCH2CO2H + CH3CO2H}}}$

## 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.[8] Acetylation of resveratrol holds promise as one of the first anti-radiation medicines for human populations.[9]

## History

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.