Acetyl group

Acetyl group
Names
	IUPAC name Acetyl (preferred to ethanoyl)
	Systematic IUPAC name Methyloxidocarbon(•) (additive)
Identifiers
CAS Number	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;
Properties
Chemical formula	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). verify (what is ?) Infobox references

In organic chemistry, an acetyl group is a functional group denoted by 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, an acetyl group is called an ethanoyl group.

An acetyl group contains a methyl group (−CH₃) that is single-bonded to a carbonyl (C=O), making it an acyl group. The carbonyl center of an acyl radical has one non-bonded electron with which it forms a chemical bond to the remainder (denoted with the letter 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

The process of adding an acetyl group into a molecule is called acetylation. An example of an acetylation reaction is the conversion of glycine to N-acetylglycine:^[7]

H₂NCH₂CO₂H + (CH₃CO)₂O → CH₃C(O)NHCH₂CO₂H + CH₃CO₂H

In biology

Enzymes which perform acetylation on proteins or other biomolecules are known as acetyltransferases. In biological organisms, acetyl groups are commonly transferred from acetyl-CoA to other organic molecules. Acetyl-CoA is an intermediate 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.^[8]

Proteins are often modified via acetylation, for various purposes. For example, acetylation of histones by histone acetyltransferases (HATs) results in an expansion of local chromatin structure, allowing transcription to occur by enabling RNA polymerase to access DNA. However, removal of the acetyl group by histone deacetylases (HDACs) condenses the local chromatin structure, thereby preventing transcription.^[9]

In synthetic organic and pharmaceutical chemistry

Acetylation can be achieved by chemists 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.

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 "acetyl" was coined by the German chemist Justus von Liebig in 1839 CE to describe what he incorrectly believed to be the radical of acetic acid (the main component of vinegar, aside from water), which is now known as the vinyl group (coined in 1851 CE); "acetyl" is derived from the Latin acētum, meaning "vinegar." When it was shown that Liebig's theory was wrong and acetic acid had a different radical, his name was carried over to the correct one, but the name of acetylene (coined in 1860 CE) was retained.^[12]

References

^ "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.
^ "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.
^ 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.
^ "Acetyl". Chemical Entities of Biological Interest. UK: European Bioinformatics Institute.
^ Banik, Gregory M.; Baysinger, Grace; Kamat, Prashant V.; Pienta, Norbert, eds. (January 2020). The ACS Guide to Scholarly Communication. Washington, DC: American Chemical Society. doi:10.1021/acsguide.50308. ISBN 978-0-8412-3586-1. S2CID 262269861.
^ Hanson, James A. (2001). Functional group chemistry. Cambridge, Eng: Royal Society of Chemistry. p. 11. ISBN 0-85404-627-5.
^ Herbst, R. M.; Shemin, D. (1943). "Acetylglycine". Organic Syntheses; Collected Volumes, vol. 2, p. 11.
^ Patel, Mulchand (June 13, 2014). "The Pyruvate Dehydrogenase Complexes: Structure-based Function and Regulation". The Journal of Biological Chemistry. 289 (24): 16615–16623. doi:10.1074/jbc.R114.563148. PMC 4059105. PMID 24798336.
^ Nelson, David L.; Cox, Michael M. (2000). Lehninger principles of biochemistry (3rd ed.). New York: Worth Publishers. ISBN 1-57259-153-6.
^ 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.
^ 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.
^ Constable, Edwin C.; Housecroft, Catherine E. (2020-04-20). "Before Radicals Were Free – the Radical Particulier of de Morveau". Chemistry. 2 (2): 293–304. doi:10.3390/chemistry2020019. ISSN 2624-8549.

[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] Banik, Gregory M.; Baysinger, Grace; Kamat, Prashant V.; Pienta, Norbert, eds. (January 2020). The ACS Guide to Scholarly Communication. Washington, DC: American Chemical Society. doi:10.1021/acsguide.50308. ISBN 978-0-8412-3586-1. S2CID 262269861.

[isbn0-85404-627-5-6] Hanson, James A. (2001). Functional group chemistry. Cambridge, Eng: Royal Society of Chemistry. p. 11. ISBN 0-85404-627-5.

[7] Herbst, R. M.; Shemin, D. (1943). "Acetylglycine". Organic Syntheses; Collected Volumes, vol. 2, p. 11.

[8] Patel, Mulchand (June 13, 2014). "The Pyruvate Dehydrogenase Complexes: Structure-based Function and Regulation". The Journal of Biological Chemistry. 289 (24): 16615–16623. doi:10.1074/jbc.R114.563148. PMC 4059105. PMID 24798336.

[9] Nelson, David L.; Cox, Michael M. (2000). Lehninger principles of biochemistry (3rd ed.). New York: Worth Publishers. ISBN 1-57259-153-6.

[10] 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.

[11] 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.

[12] Constable, Edwin C.; Housecroft, Catherine E. (2020-04-20). "Before Radicals Were Free – the Radical Particulier of de Morveau". Chemistry. 2 (2): 293–304. doi:10.3390/chemistry2020019. ISSN 2624-8549.

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