{{Short description|1=Chemical group, –C(=O)CH3}} {{Distinguish|Acetal}} {{Chembox | Verifiedfields = changed | Watchedfields = changed | verifiedrevid = 4772398727 | ImageFile = Acetyl group.svg | ImageFile_Ref = {{chemboximage|correct|??}} | ImageSize = 121 | ImageName = Skeletal formula of acetyl with all implicit hydrogens shown | IUPACName = Acetyl (preferred to ethanoyl)<ref>{{Cite web|url = http://www.acdlabs.com/iupac/nomenclature/79/r79_1037.htm|title = List of Radical Names Beginning from "A" |work = Nomenclature of Organic Chemistry, Sections A, B, C, D, E, F, and H, Pergamon Press, Oxford, 1979. Copyright 1979 IUPAC}}</ref><ref>{{Cite web|url = http://www.acdlabs.com/iupac/nomenclature/93/r93_480.htm|title = R-5.7.1 Carboxylic acids, where acetyl appears as an example |work = IUPAC, Commission on Nomenclature of Organic Chemistry. A Guide to IUPAC Nomenclature of Organic Compounds (Recommendations 1993), 1993, Blackwell Scientific publications, Copyright 1993 IUPAC }}</ref><ref>{{BlueBook2013|rec=65.1.7.2.1}}</ref> | SystematicName = Methyloxidocarbon(•)<ref>{{Cite web|url = https://www.ebi.ac.uk/chebi/searchId.do?chebiId=46887|title = Acetyl|work = Chemical Entities of Biological Interest|location = UK|publisher = European Bioinformatics Institute}}</ref> (additive) | Section1 = {{Chembox Identifiers | Abbreviations = Ac | CASNo_Ref = {{cascite|changed|??}} | CASNo = 3170-69-2 | PubChem = 137849 | ChemSpiderID = 121499 | ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} | ChEBI_Ref = {{ebicite|correct|EBI}} | ChEBI = 46887 | Beilstein = 1697938 | Gmelin = 786 | SMILES = C[C]=O | StdInChI = 1S/C2H3O/c1-2-3/h1H3 | StdInChI_Ref = {{stdinchicite|correct|chemspider}} | StdInChIKey = TUCNEACPLKLKNU-UHFFFAOYSA-N | StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} }} | Section2 = {{Chembox Properties | C=2 | H=3 | O=1 }} | Section3 = {{Chembox Thermochemistry | DeltaHf = −15 to −9 kJ mol<sup>−1</sup> }} | Section4 = {{Chembox Related | OtherCompounds = Acetone<br>Carbon monoxide<br>Acetic acid }} }}
In organic chemistry, an '''acetyl group''' is a functional group denoted by the chemical formula {{chem2|\sCOCH3}} and the structure {{chem2|\sC(\dO)\sCH3}}. It is sometimes represented by the symbol '''Ac'''<ref>{{Cite book |url=https://pubs.acs.org/doi/book/10.1021/acsguide |title=The ACS Guide to Scholarly Communication |date=January 2020 |publisher=American Chemical Society |isbn=978-0-8412-3586-1 |editor-last=Banik |editor-first=Gregory M. |location=Washington, DC |language=en |doi=10.1021/acsguide.50308 |s2cid=262269861 |editor-last2=Baysinger |editor-first2=Grace |editor-last3=Kamat |editor-first3=Prashant V. |editor-last4=Pienta |editor-first4=Norbert}}</ref><ref name="isbn0-85404-627-5">{{cite book |author=Hanson, James A. |title=Functional group chemistry |publisher=Royal Society of Chemistry |location=Cambridge, Eng |year=2001 |pages=11 |isbn=0-85404-627-5 }}</ref> (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 ({{chem2|\sCH3}}) that is single-bonded to a carbonyl ({{chem2|C\dO}}), making it an acyl group.
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== {{main|Acetylation}} Acetylation is the chemical reaction known as "ethanoylation" in the IUPAC nomenclature. It depicts a reactionary process that injects an acetyl functional group into a chemical compound. The opposite reaction is called "'''de'''acetylation", and this is the '''removal''' of the acetyl group. An example of an acetylation reaction is the conversion of glycine to ''N''-acetylglycine:<ref>{{OrgSynth|first1=R. M.|last1=Herbst|first2=D.|last2=Shemin|title=Acetylglycine|collvol=2|collvolpages=11|year=1943|prep=CV2P0011}}</ref> :{{chem2 | 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.<ref>{{Cite journal |last=Patel |first=Mulchand |date=June 13, 2014 |title=The Pyruvate Dehydrogenase Complexes: Structure-based Function and Regulation |journal=The Journal of Biological Chemistry |volume=289 |issue=24 |pages=16615–16623 |doi=10.1074/jbc.R114.563148 |doi-access=free |pmid=24798336 |pmc=4059105 }}</ref>
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.<ref>{{cite book|first1=David L.|last1=Nelson |first2=Michael M.|last2=Cox|title=Lehninger principles of biochemistry|date=2000|publisher=Worth Publishers|location=New York|isbn=1-57259-153-6|edition=3rd|url-access=registration|url=https://archive.org/details/lehningerprincip01lehn}}</ref>
===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. Acetic anhydride and acetyl chloride are good candidates for acetylation for two reasons: the electrophilicity of the carbonyl carbon of the acetyl group is enhanced by the electron-withdrawing inductive effect of the neighbouring group (acetoxy- and chloro-, respectively), and the leaving group is stable or stabilised through resonance (acetate and chloride, respectively). The amine base is primarily used to capture free protons, but may also further activate the acetyl group towards nucleophilic attack.<ref>{{Cite web |date=2023-07-23 |title=21.5: Chemistry of Acid Anhydrides |url=https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Organic_Chemistry_(OpenStax)/21%3A_Carboxylic_Acid_Derivatives-_Nucleophilic_Acyl_Substitution_Reactions/21.05%3A_Chemistry_of_Acid_Anhydrides |access-date=2026-01-07 |website=Chemistry LibreTexts |language=en}}</ref><ref>{{Cite web |title=Acetyl Chloride |url=https://commonorganicchemistry.com/Common_Reagents/Acetyl_Chloride/Acetyl_Chloride.htm |access-date=2026-01-07 |website=commonorganicchemistry.com}}</ref>
For example, salicylic acid can be acetylated by acetic anhydride to form aspirin:<ref>{{Cite web |title=Synthesis of aspirin on a microscale |url=https://edu.rsc.org/experiments/synthesis-of-aspirin-on-a-microscale/556.article |access-date=2026-01-07 |website=RSC Education |language=en}}</ref>
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==Pharmacology== Acetylated organic molecules exhibit increased ability to cross the selectively permeable blood–brain barrier.<ref name=":0">{{Cite journal |last=Pardridge |first=William M |date=2012-08-29 |title=Drug Transport across the Blood–Brain Barrier |journal=Journal of Cerebral Blood Flow & Metabolism |language=en |volume=32 |issue=11 |pages=1959–1972 |doi=10.1038/jcbfm.2012.126 |pmid=22929442 |issn=0271-678X |pmc=3494002 }}</ref> 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|date=January 2016}} 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).<ref name=":0" />
There is some evidence that acetyl-<small>L</small>-carnitine may be more effective for some applications than <small>L</small>-carnitine.<ref>{{Cite journal | pmid = 15591009 | year = 2004 | last1 = Liu | first1 = J | title = 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 | journal = Annals of the New York Academy of Sciences | volume = 1033 | issue = 1 | pages = 117–31 | last2 = Head | first2 = E | last3 = Kuratsune | first3 = H | last4 = Cotman | first4 = C. W. | last5 = Ames | first5 = B. N. | s2cid = 24221474 | doi = 10.1196/annals.1320.011 | bibcode = 2004NYASA1033..117L }}</ref> Acetylation of resveratrol holds promise as one of the first anti-radiation medicines for human populations.<ref>{{cite journal|last1=Koide|first1=Kazunori|last2=Osman|first2=Sami|last3=Garner|first3=Amanda L.|last4=Song|first4=Fengling|last5=Dixon|first5=Tracy|last6=Greenberger|first6=Joel S.|last7=Epperly|first7=Michael W.|title=The Use of 3,5,4′-Tri-acetylresveratrol as a Potential Prodrug for Resveratrol Protects Mice from γ-Irradiation-Induced Death|journal=ACS Medicinal Chemistry Letters|date=14 April 2011|volume=2|issue=4|pages=270–274|doi=10.1021/ml100159p|pmid=21826253|pmc=3151144}}</ref>
== Etymology == The term "acetyl" was coined by the German chemist Justus von Liebig in 1839 to describe what is now known as the vinyl group (coined in 1851). He and others before him regarded this group (groups were called radicals at that time) as the basis for other C2 compounds including acetic acid (the main component of vinegar, aside from water), Later the name was carried over to the MeCO-group used today, but the name of acetylene (coined in 1860) was retained.<ref>{{Cite journal |last1=Constable |first1=Edwin C. |last2=Housecroft |first2=Catherine E. |date=2020-04-20 |title=Before Radicals Were Free – the Radical Particulier of de Morveau |journal=Chemistry |language=en |volume=2 |issue=2 |pages=293–304 |doi=10.3390/chemistry2020019 |issn=2624-8549 |doi-access=free}}</ref> "Acetyl" is derived from the Latin ''acētum,'' meaning "vinegar.", and the Greek ''Húlē,'' meaning substance, or material.<ref>{{Cite web |date=2025-12-24 |title=Definition of ACETYL |url=https://www.merriam-webster.com/dictionary/acetyl |access-date=2026-01-10 |website=www.merriam-webster.com |language=en}}</ref> ==See also== * Acetaldehyde * Acetoxy group * Histone acetylation and deacetylation * Polyoxymethylene plastic (acetal resin), a thermoplastic
==References== {{Reflist}}
{{Functional group}}
Category:Acyl groups