View source for Acetate

{{Short description|Salt formed from acetic acid and a base}}
{{Other uses}}
{{Not to be confused|Acetone}}
{{Chembox
|ImageFile = Acetate-anion-3D-balls.png
|ImageAlt = [[Ball-and-stick model]] of the acetate anion
|SystematicName = Ethanoate
|IUPACName = Acetate
|Section1={{Chembox Identifiers
|CASNo = 71-50-1
|CASNo_Ref = {{cascite|correct|CAS}}
| ChEBI = 30089
| DrugBank = DB14511
|ChemSpiderID = 170
|PubChem = 175
|UNII_Ref = {{fdacite|correct|FDA}}
|UNII = 569DQM74SC
|SMILES = CC(=O)[O-]
|InChI = 1/C2H4O2/c1-2(3)4/h1H3,(H,3,4)/p-1
|InChIKey = QTBSBXVTEAMEQO-REWHXWOFAL
|StdInChI = 1S/C2H4O2/c1-2(3)4/h1H3,(H,3,4)/p-1
|StdInChIKey = QTBSBXVTEAMEQO-UHFFFAOYSA-M
}}
|Section2={{Chembox Properties
| C=2|H=3|O=2|Formula_Charge=- 
|ConjugateAcid = [[Acetic acid]]
}}
}}

An '''acetate''' is a [[salt (chemistry)|salt]] formed by the combination of [[acetic acid]] with a base (e.g. [[Alkali metal|alkaline]], [[Alkaline earth metal|earthy]], [[Transition metal|metallic]], [[Nonmetal (chemistry)|nonmetal]]lic, or radical [[Radical (chemistry)|base]]). "Acetate" also describes the [[conjugate acid|conjugate base]] or [[ion]] (specifically, the negatively charged ion called an [[anion]]) typically found in [[aqueous solution]] and written with the chemical formula {{chem|C|2|H|3|O|2|-}}. The neutral molecules formed by the combination of the acetate ion and a ''positive'' ion (called a [[cation]]) are also commonly called "acetates" (hence, ''acetate of lead'', ''acetate of aluminium'', etc.). The simplest of these is hydrogen acetate (called [[acetic acid]]) with corresponding salts, [[ester]]s, and the [[polyatomic ion|polyatomic anion]] {{chem|CH|3|CO|2|-}}, or {{chem|CH|3|COO|-}}.

Most of the approximately 5 million tonnes of acetic acid produced annually in industry are used in the production of acetates, which usually take the form of [[polymers]]. In nature, acetate is the most common building block for [[biosynthesis]].

==Nomenclature and common formula==
When part of a [[salt (chemistry)|salt]], the formula of the acetate ion is written as {{chem|CH|3|CO|2|-}}, {{chem|C|2|H|3|O|2|-}}, or {{chem|CH|3|COO|-}}. Chemists often represent acetate as OAc<sup>−</sup> or, less commonly, AcO<sup>−</sup>. Thus, HOAc is the symbol for acetic acid, NaOAc for [[sodium acetate]], and EtOAc for [[ethyl acetate]]<ref name=Zum>Zumdahl, S. S. "Chemistry" Heath, 1986: Lexington, MA.  {{ISBN|0-669-04529-2}}.</ref> (as Ac is common symbol for [[acetyl]] group CH<sub>3</sub>CO<ref>{{RedBook2005|page=63}}</ref><ref>{{cite journal |last1=Brimble |first1=Margaret A. |last2=Black |first2=David StC. |last3=Hartshorn |first3=Richard |last4=Rauter |first4=Amélia P. |last5=Sha |first5=Chin-Kang |last6=Sydnes |first6=Leiv K. |title=Rules for abbreviation of protecting groups (IUPAC Technical Report) |journal=Pure and Applied Chemistry |date=10 November 2012 |volume=85 |issue=1 |page=310 |doi=10.1351/PAC-REP-12-07-12|s2cid=55102299 |doi-access=free }}</ref>). The [[pseudoelement symbol]] "Ac" is also sometimes encountered in chemical formulas as indicating the entire acetate ion ({{chem|CH|3|CO|2|-}}).{{citation needed|date=August 2019}} It is not to be confused with the symbol of [[actinium]], the first element of the [[actinide]] series; context guides disambiguation. For example, the formula for sodium acetate might be abbreviated as "NaOAc", rather than "NaC<sub>2</sub>H<sub>3</sub>O<sub>2</sub>". Care should also be taken to avoid confusion with [[peracetic acid]] when using the OAc abbreviation; for clarity and to avoid errors when translated, HOAc should be avoided in literature mentioning both compounds.

Although its [[systematic name]] is ''ethanoate'' ({{IPAc-en|ᵻ|ˈ|θ|æ|n|oʊ|.|eɪ|t}}), the common ''acetate'' remains the [[preferred IUPAC name]].<ref>[http://www.acdlabs.com/iupac/nomenclature/93/r93_671.htm R-9.1 Trivial and semisystematic names retained for naming organic compounds] {{Webarchive|url=https://web.archive.org/web/20140208214014/http://www.acdlabs.com/iupac/nomenclature/93/r93_671.htm |date=2014-02-08 }}, ''A Guide to IUPAC Nomenclature of Organic Compounds'', IUPAC Commission on Nomenclature of Organic Chemistry</ref>

==Salts==
[[Image:Acetate-anion-canonical-form-2D-skeletal.png|class=skin-invert-image|thumb|100px|acetate anion]]
The acetate [[anion]], [CH<sub>3</sub>COO]<sup>−</sup>,(or [C<sub>2</sub>H<sub>3</sub>O<sub>2</sub>]<sup>−</sup>) is one of the [[carboxylate]] family. It is the [[conjugate acid|conjugate base]] of [[acetic acid]]. Above a pH of 5.5, acetic acid converts to acetate:<ref name=Zum/>
:CH<sub>3</sub>COOH ⇌ CH<sub>3</sub>COO<sup>−</sup> + H<sup>+</sup>
Many acetate salts are ionic, indicated by their tendency to dissolve well in water. A commonly encountered acetate in the home is [[sodium acetate]], a white solid that can be prepared by combining vinegar and [[sodium bicarbonate]] ("bicarbonate of soda"):

:CH<sub>3</sub>COOH  +  NaHCO<sub>3</sub>  →   CH<sub>3</sub>COO<sup>−</sup>Na<sup>+</sup>  +  H<sub>2</sub>O  +  CO<sub>2</sub>

[[Transition metal]]s can be complexed by acetate. Examples of acetate complexes include [[chromium(II) acetate]] and basic zinc acetate.

Commercially important acetate salts are [[aluminium acetate]], used in [[dyeing]], [[ammonium acetate]], a precursor to [[acetamide]], and [[potassium acetate]], used as a [[diuretic]]. All three salts are colourless and highly soluble in water.<ref name=Ull>Hosea Cheung, Robin S. Tanke, G. Paul Torrence "Acetic acid" in ''Ullmann's Encyclopedia of Industrial Chemistry''  Weinheim, Germany: Wiley-VCH, 2005. {{doi|10.1002/14356007.a01_045}}</ref>

==Esters==
[[Image:Acetate-ester-2D-skeletal.png|class=skin-invert-image|thumb|100px|acetate ester]]
Acetate [[ester]]s have the general formula CH<sub>3</sub>CO<sub>2</sub>R, where R is an [[substituent|organyl group]]. The esters are the dominant forms of acetate in the marketplace. Unlike the acetate salts, acetate esters are often liquids, lipophilic, and sometimes volatile. They are popular because they have inoffensive, often sweet odors, they are inexpensive, and they are usually of low toxicity.

Almost half of acetic acid production is consumed in the production of [[vinyl acetate]], precursor to [[polyvinyl alcohol]], which is a component of many [[paint]]s. The second largest use of acetic acid is consumed in the production of [[cellulose acetate]]. In fact, "acetate" is jargon for cellulose acetate, which is used in the production of fibres or diverse products, e.g. the [[acetate disc]]s used in audio record production. Cellulose acetate can be found in many household products. Many industrial [[solvent]]s are acetates, including [[methyl acetate]], ethyl acetate, [[isopropyl acetate]], and ethylhexyl acetate. [[Butyl acetate]] is a fragrance used in food products.<ref name=Ull/>

==Acetate in biology==
Acetate is a common anion in biology. It is mainly utilized by organisms in the form of [[Acetyl-CoA|acetyl coenzyme A]].<ref>Nelson, D. L.; Cox, M. M. "Lehninger, Principles of Biochemistry" 3rd Ed. Worth Publishing: New York, 2000. {{ISBN|1-57259-153-6}}.</ref>

[[Intraperitoneal injection]] of [[sodium acetate]] (20 or 60&nbsp;mg per kg body mass) was found to induce headache in sensitized rats, and it has been proposed that acetate resulting from oxidation of [[ethanol]] is a major factor in causing [[hangover]]s. Increased serum acetate levels lead to accumulation of [[adenosine]] in many tissues including the brain, and administration of the [[adenosine]] receptor antagonist [[caffeine]] to rats after ethanol was found to decrease [[nociceptive]] behavior.<ref>{{cite journal | last1 = Maxwell | first1 = Christina | display-authors = etal | year = 2010| title = Acetate Causes Alcohol Hangover Headache in Rats | journal = PLOS ONE | volume = 5 | issue = 12| article-number = e15963 | doi=10.1371/journal.pone.0015963 | pmid=21209842 | pmc=3013144| bibcode = 2010PLoSO...515963M| doi-access = free }}</ref><ref>[https://www.newscientist.com/article/dn19942-is-coffee-the-real-cure-for-a-hangover.html 'Is coffee the real cure for a hangover?'] by Bob Holmes, [[New Scientist]], Jan. 15 2011, p. 17.</ref>

Acetate has known [[immunomodulatory]] properties and can affect the innate [[Immune system|immune]] response to [[Pathogenic bacteria|pathogenic]] bacteria such as the respiratory pathogen ''Haemophilus influenzae''.<ref>{{Cite journal|last1=Hosmer|first1=Jennifer|last2=Nasreen|first2=Marufa|last3=Dhouib|first3=Rabeb|last4=Essilfie|first4=Ama-Tawiah|last5=Schirra|first5=Horst Joachim|last6=Henningham|first6=Anna|last7=Fantino|first7=Emmanuelle|last8=Sly|first8=Peter|last9=McEwan|first9=Alastair G.|last10=Kappler|first10=Ulrike|date=2022-01-27|title=Access to highly specialized growth substrates and production of epithelial immunomodulatory metabolites determine survival of Haemophilus influenzae in human airway epithelial cells|journal=PLOS Pathogens|language=en|volume=18|issue=1|article-number=e1010209|doi=10.1371/journal.ppat.1010209|pmid=35085362 |issn=1553-7374|pmc=8794153 |doi-access=free }}</ref>

==Fermentation of acetyl CoA to acetate==
Pyruvate is converted into [[acetyl-CoA|acetyl-coenzyme A (acetyl-CoA)]] by the enzyme [[pyruvate dehydrogenase]]. This acetyl-CoA is then converted into acetate in ''E. coli'', whilst producing ATP by [[substrate-level phosphorylation]]. Acetate formation requires two enzymes: phosphate acetyltransferase and acetate kinase.<ref name="Keseler2011">{{Cite journal | author=Keseler, Ingrid M. | title=EcoCyc: a comprehensive database of Escherichia coli biology | journal=[[Nucleic Acids Research]] | volume= 39| year=2011 | issue=Database issue | doi=10.1093/nar/gkq1143|display-authors=etal | pmid=21097882 | pmc=3013716 | pages=D583–D590}}</ref>
[[File:E. coli Bacteria (7316101966).jpg|thumb|300px|The mixed acid fermentation pathway is characteristic of the family [[Enterobacteriaceae]], which includes ''E. coli'']]

&nbsp; &nbsp; &nbsp; acetyl-CoA + phosphate → acetyl-phosphate + CoA

&nbsp; &nbsp; &nbsp; acetyl-phosphate + ADP → acetate + ATP

==Fermentation of acetate==

Acetic acid can also undergo a [[dismutation]] reaction to produce [[methane]] and [[carbon dioxide]]:<ref>{{Cite journal| last = Ferry| first = J.G.| year = 1992| title = Methane from acetate| journal = Journal of Bacteriology
| volume = 174| issue = 17| pages = 5489–5495
| doi = 10.1128/jb.174.17.5489-5495.1992| pmid = 1512186| url= | pmc = 206491}}</ref><ref>{{Cite book | last1 = Vogels | first1 = G. D.| last2 = Keltjens |first2= J. T.|last3=Van Der Drift |first3= C.| year = 1988 | chapter = Biochemistry of methane production | editor = Zehnder A.J.B. |editor-link=Alexander Zehnder | title = Biology of anaerobic microorganisms | publisher = Wiley
| place = New York| pages = 707–770}}</ref>

:CH<sub>3</sub>COO<sup>−</sup> + H<sup>+</sup> → CH<sub>4</sub> + CO<sub>2</sub> {{pad|3em}} Δ''G''° = −36&nbsp;kJ/mol

This [[disproportionation]] reaction is catalysed by [[methanogen]] [[archaea]] in their fermentative metabolism. One electron is transferred from the [[carbonyl]] function ([[electron donor|e<sup>−</sup> donor]]) of the [[carboxylic]] group to the [[methyl]] group ([[electron acceptor|e<sup>−</sup> acceptor]]) of acetic acid to respectively produce CO<sub>2</sub> and methane gas.

==Structures==
<gallery class=skin-invert-image>
Image:Acetate-anion-3D-vdW.png|{{center|[[Space-filling model]] of the acetate anion}}
Image:Acetate-anion-resonance-hybrid-2D-skeletal.png|{{center|[[resonance (chemistry)|resonance hybrid]] of the acetate anion}}
Image:Acetate-resonance-2D-skeletal.png|{{center|[[resonance (chemistry)|canonical forms]] of the acetate anion}}
</gallery>

== See also ==
* [[Acetic acid]]
*   [[      Acetoxy  group  ]]           
* [[Acetyl chloride]]
* [[Acetylation]]
* [[Cellulose acetate]]
* [[Copper(II) acetate]]
* [[Fermentation (biochemistry)]]
* [[Mixed acid fermentation]]
* [[Sodium acetate]]
* [[Zinc acetate]]

==References==
{{Reflist}}

== External links ==
{{Commons category     inline  }}

{{Acetates}}
{{Authority control}}

[[Category:Acetates| ]]
[[Category:Carboxylate anions]]
[[Category:Leaving groups]]