acetate anion

acetate ester

An acetate /ˈæsɪteɪt/ is a derivative of acetic acid. This term includes salts and esters, as well as the anion found in solution. 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 C2 units derived from acetate.^[1]

Nomenclature and common formula[link]

When part of a salt, the formula of the acetate anion 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 "CH₃COONa". 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[link]

The acetate (poo) anion, [CH₃COO]⁻, 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 ("bicarb"):

CH₃COOH + NaHCO₃ → CH₃COO⁻Na⁺ + H₂O + CO₂

Transition metals can be complexed by acetate. Acetate is considered a relatively weak ligand in coordination chemistry because it can only form monodentate complexes. 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[link]

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[link]

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[link]

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

CH₃COO^– + H⁺ → CH₄ + CO₂       ΔG° = -36 kJ/reaction

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[link]

• 

  space-filling model of the acetate anion
• 

  ball-and-stick model of the acetate anion
• 

  resonance hybrid of the acetate anion
• 

  canonical forms of the acetate anion

See also[link]

Wikimedia Commons has media related to: acetates

• Acetic acid
• Acetylation
• Cellulose acetate
• Copper(II) acetate
• Fermentation (biochemistry)
• Sodium acetate

References[link]

John McLane by Daniel Strain

John McLane (February 27, 1852–April 13, 1911) was a furniture maker and politician from Milford, New Hampshire. He was Governor of New Hampshire from 1905 to 1907.

He was born in Lennoxtown, in Scotland, the son of Alexander McLane and his wife Mary, née Hay, and was brought to America with his family in 1853, when he was one year old. They settled in Manchester, and moved to Milford in 1869. Upon completion of his schooling, he became a cabinetmaker's apprentice, and opened his own shop in 1876. The business's success (it was for a time the largest manufacture of post-office furniture in North America) secured other business opportunities for him: he became a director of the Milford Granite Company, the Souheagan National Bank and the New Hampshire Fire Insurance Company.

On 10 March 1880 he married Ellen Luetta Tuck (1855–1927). They had four children, Clinton Averill McLane (1881), Hazel Ellen McLane (1885), John Roy McLane (1886), and Charles Malcolm McLane (1910).

McLane was elected, as a Republican, to the New Hampshire House of Representatives in 1885, and to the New Hampshire Senate in 1891, representing the 16th District 1891-92 and the 15th District 1893-94. He was president of the senate during his two terms. He was a delegate to the Republican National Convention from New Hampshire in 1900, and was elected governor in 1904.

As governor, McLane was instrumental in securing funding for highway improvement, and welcomed delegates to the Russo-Japanese War Peace Conference, which was held in Portsmouth during his term in office.

He died in Pinehurst, Moore County, North Carolina, and was interred at the Milford Cemetery, Milford, New Hampshire.

References[link]

External links[link]

• McLane at New Hampshire's Division of Historic Resources

v t e Governors of New Hampshire Weare Langdon Sullivan Langdon Sullivan J. Bartlett Gilman Langdon J. Smith Langdon Plumer Gilman Plumer S. Bell Woodbury Morril Pierce J. Bell Pierce Harvey Dinsmoor Badger Hill Page Hubbard Steele Colby Williams Dinsmoor Jr. Martin Baker Metcalf Haile Goodwin Berry Gilmore Smyth Harriman Stearns Weston Straw Weston Cheney Prescott Head C. Bell Hale Currier Sawyer Goodell Tuttle J. B. Smith Busiel Ramsdell Rollins Jordan Bachelder McLane Floyd Quinby Bass Felker R. Spaulding Keyes J. H. Bartlett A. Brown F. Brown Winant H. Spaulding Tobey Winant Bridges Murphy Blood Dale Adams H. Gregg Dwinell Powell King Peterson Thomson Gallen Roy Sununu J. Gregg Merrill Shaheen Benson Lynch