Acetyl group

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 rarely heard.

Not to be confused with Acetal.
Acetyl group
Skeletal formula of acetyl with all implicit hydrogens shown
Names
IUPAC name
Acetyl (preferred to ethanoyl)[1][2][3]
Systematic IUPAC name
Methyloxidocarbon(•)[4] (additive)
Identifiers
3D model (JSmol)
Abbreviations Ac
1697938
ChEBI
ChemSpider
786
  • InChI=1S/C2H3O/c1-2-3/h1H3 checkY
    Key: TUCNEACPLKLKNU-UHFFFAOYSA-N checkY
  • C[C]=O
Properties
C2H3O
Molar mass 43.045 g·mol−1
Thermochemistry
−15 to −9 kJ mol−1
Related compounds
Related compounds
 Acetone

Carbon monoxide

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)
Infobox references

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.

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]

Pharmacology

Acetylated organic molecules exhibit increased ability to cross the selectively permeable blood–brain barrier. 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. 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.

See also

References
  1. "List of Radical Names Beginning from "A"". Nomenclature of Organic Chemistry, Sections A, B, C, D, E, F, and H, Pergamon Press, Oxford, 1979. Copyright 1979 IUPAC.
  2. "R-5.7.1 Carboxylic acids, where acetyl appears as an example". IUPAC, Commission on Nomenclature of Organic Chemistry. A Guide to IUPAC Nomenclature of Organic Compounds (Recommendations 1993), 1993, Blackwell Scientific publications, Copyright 1993 IUPAC.
  3. IUPAC Chemical Nomenclature and Structure Representation Division (2013). "P-65.1.7.2.1". In Favre, Henri A.; Powell, Warren H. (eds.). Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013. IUPAC–RSC. ISBN 978-0-85404-182-4.
  4. "Acetyl". Chemical Entities of Biological Interest. UK: European Bioinformatics Institute.
  5. Hanson, James A. (2001). Functional group chemistry. Cambridge, Eng: Royal Society of Chemistry. p. 11. ISBN 0-85404-627-5.
  6. Cox, David L. Nelson, Michael M. (2000). Lehninger principles of biochemistry (3rd ed.). New York: Worth Publishers. ISBN 1-57259-153-6.{{cite book}}: CS1 maint: multiple names: authors list (link)
  7. R. M. Herbst and D. Shemin (1943). "Acetylglycine". Organic Syntheses.; Collective Volume, vol. 2, p. 11
  8. Liu, J; Head, E; Kuratsune, H; Cotman, C. W.; Ames, B. N. (2004). "Comparison of the effects of L-carnitine and acetyl-L-carnitine on carnitine levels, ambulatory activity, and oxidative stress biomarkers in the brain of old rats". Annals of the New York Academy of Sciences. 1033 (1): 117–31. Bibcode:2004NYASA1033..117L. doi:10.1196/annals.1320.011. PMID 15591009. S2CID 24221474.
  9. Koide, Kazunori; Osman, Sami; Garner, Amanda L.; Song, Fengling; Dixon, Tracy; Greenberger, Joel S.; Epperly, Michael W. (14 April 2011). "The Use of 3,5,4′-Tri-acetylresveratrol as a Potential Prodrug for Resveratrol Protects Mice from γ-Irradiation-Induced Death". ACS Medicinal Chemistry Letters. 2 (4): 270–274. doi:10.1021/ml100159p. PMC 3151144. PMID 21826253.
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