World Library  
Flag as Inappropriate
Email this Article

Acetate

Article Id: WHEBN0000194637
Reproduction Date:

Title: Acetate  
Author: World Heritage Encyclopedia
Language: English
Subject: Mukaiyama Taxol total synthesis, Cellulose acetate, Acid dissociation constant, List of PET radiotracers, Eastman Kodak Co v. Harold Worden
Collection: Acetates, Carboxylate Anions
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Acetate

Acetate
Ball-and-stick model of the acetate anion
Names
IUPAC name
Acetate
Systematic IUPAC name
Ethanoate
Identifiers
ChemSpider
Jmol-3D images Image
PubChem
Properties
CH
3
CO
2
Molar mass 59.04 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Acetate is a negative ion, or anion, typically found in aqueous solution. It is often written with the chemical formula C2H3O2. The neutral molecules formed by the combination of the acetate ion and a positive ion (or cation) are also commonly called "acetates". The simplest of these is hydrogen acetate, or acetic acid, with corresponding salts, esters, and the polyatomic anion CH3CO2, or CH3COO.

Most of the approximately 5 billion kilograms 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. For example, the fatty acids are produced by connecting the two carbon atoms from acetate to a growing fatty acid.[1]

Contents

  • Nomenclature and common formula 1
  • Salts 2
  • Esters 3
  • Acetate in biology 4
  • Fermentation of acetate 5
  • Structures 6
  • See also 7
  • References 8
  • External links 9

Nomenclature and common formula

When part of a salt, the formula of the acetate ion is written as CH3CO2, C2H3O2, or CH3COO. Chemists abbreviate acetate as OAc or AcO. Thus, HOAc is the abbreviation for acetic acid, NaOAc for sodium acetate, and EtOAc for ethyl acetate.[2] The abbreviation "Ac" (or "AC") is also sometimes encountered in chemical formulas to indicate the acetate ion. This abbreviation is not to be confused with the symbol of actinium, the first element of the actinides series. For example, the formula for sodium acetate might be abbreviated as "NaAc", rather than "NaC2H3O2". 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.

The systematic name for acetate is ethanoate, but the IUPAC preferred name remains the common name, acetate.[3]

Salts

acetate anion

The acetate anion, [CH3COO],(or [C2H3O2]) is one of the carboxylate family. It is the conjugate base of acetic acid. Above a pH of 5.5, acetic acid converts to acetate:[2]

CH3COOH CH3COO + H+

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"):

CH3COOH + NaHCO3 → CH3COONa+ + H2O + CO2

Transition metals 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.[4]

Esters

acetate ester

Acetate esters have the general formula CH3CO2R, where R is an 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 paints. 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 discs used in audio record production. Cellulose acetate can be found in many household products. Many industrial solvents are acetates, including methyl acetate, ethyl acetate, isopropyl acetate, ethylhexyl acetate. Butyl acetate is a fragrance used in food products.[4]

Acetate in biology

Acetate is a common anion in biology. It is mainly utilized by organisms in the form of acetyl coenzyme A.[5]

Intraperitoneal injection of sodium acetate (20 or 60 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 hangovers. 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.[6][7]

Fermentation of acetate

Acetic acid can also undergo a dismutation reaction to produce methane and carbon dioxide:[8][9]

CH3COO + H+ → CH4 + CO2       ΔG° = -36 kJ/mol

This disproportionation reaction is catalysed by methanogen archaea in their fermentative metabolism. One electron is transferred from the carbonyl function (e donor) of the carboxylic group to the methyl group (e acceptor) of acetic acid to respectively produce CO2 and methane gas.

Structures

See also

References

  1. ^ March, J. “Advanced Organic Chemistry” 4th Ed. J. Wiley and Sons, 1992: New York. ISBN 0-471-60180-2.
  2. ^ a b Zumdahl, S. S. “Chemistry” Heath, 1986: Lexington, MA. ISBN 0-669-04529-2.
  3. ^ R-9.1 Trivial and semisystematic names retained for naming organic compounds, A Guide to IUPAC Nomenclature of Organic Compounds, IUPAC Commission on Nomenclature of Organic Chemistry
  4. ^ a b 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
  5. ^ Nelson, D. L.; Cox, M. M. "Lehninger, Principles of Biochemistry" 3rd Ed. Worth Publishing: New York, 2000. ISBN 1-57259-153-6.
  6. ^  
  7. ^ 'Is coffee the real cure for a hangover?' by Bob Holmes, New Scientist, Jan. 15 2011, p. 17.
  8. ^ Ferry, J.G. (1992). "Methane from acetate". Journal of Bacteriology 174 (17): 5489–5495. Retrieved 2011-11-05. 
  9. ^ Vogels, G. D.; Keltjens, J. T.; Van Der Drift, C. (1988). "Biochemistry of methane production". In Zehnder A.J.B. Biology of anaerobic microorganisms. New York: Wiley. pp. 707–770. 

External links

This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.