An acetate /ˈæsɪteɪt/ is a salt formed by the combination of acetic acid with an alkaline, earthy, or metallic base. "Acetate" also describes the conjugate base or ion (specifically, the negatively charged ion called an anion) typically found in aqueous solution and written with the chemical formula C2H3O2−. 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 aluminum, etc.). The simplest of these is hydrogen acetate (called 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 Nomenclature and common formula
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, less commonly, AcO−. Thus, HOAc is the abbreviation for acetic acid, NaOAc for sodium acetate, and EtOAc for ethyl acetate. The abbreviation "Ac" (or "AC") is also sometimes encountered in chemical formulas to indicate the acetate ion (CH3CO2−), or the acetyl group (CH3CO). This abbreviation is not to be confused with the symbol of actinium, the first element of the actinide 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. Although its systematic name is ethanoate, the common acetate remains the preferred IUPAC name . Salts
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:
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 → CH3COO−Na+ + 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. Esters
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
resonance hybrid of the acetate anion
canonical forms of the acetate anion
Acetylation Cellulose acetate Copper(II) acetate Fermentation (biochemistry) Sodium acetate
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Sons, 1992: New York. ISBN 0-471-60180-2.
^ a b Zumdahl, S. S. “Chemistry” Heath, 1986: Lexington, MA.
^ 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
^ 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
^ Nelson, D. L.; Cox, M. M. "Lehninger, Principles of Biochemistry"
3rd Ed. Worth Publishing: New York, 2000. ISBN 1-57259-153-6.
^ Maxwell, Christina; et al. (2010). "
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Acetyl halides and salts of the acetate ion
LiOAc Be(OAc)2 BeAcOH B(OAc)3 AcOAc ROAc NH4OAc AcOOH FAc Ne
NaOAc Mg(OAc)2 Al(OAc)3 ALSOL Al(OAc)2OH Al2SO4(OAc)4 Si P S ClAc Ar
KOAc Ca(OAc)2 Sc(OAc)3 Ti(OAc)4 VO(OAc)3 Cr(OAc)2 Mn(OAc)2 Mn(OAc)3 Fe(OAc)2 Fe(OAc)3 Co(OAc)2, Co(OAc)3 Ni(OAc)2 Cu(OAc)2 Zn(OAc)2 Ga(OAc)3 Ge As(OAc)3 Se BrAc Kr
RbOAc Sr(OAc)2 Y(OAc)3 Zr(OAc)4 Nb Mo(OAc)2 Tc Ru(OAc)2 Ru(OAc)3 Ru(OAc)4 Rh2(OAc)4 Pd(OAc)2 AgOAc Cd(OAc)2 In Sn(OAc)2 Sn(OAc)4 Sb(OAc)3 Te IAc Xe
CsOAc Ba(OAc)2 Hf Ta W Re Os Ir Pt(OAc)2 Au Hg2(OAc)2, Hg(OAc)2 TlOAc Tl(OAc)3 Pb(OAc)2 Pb(OAc)4 Bi(OAc)3 Po At Rn
Fr Ra Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og
La(OAc)3 Ce(OAc)x Pr Nd Pm Sm(OAc)3 Eu(OAc)3 Gd(OAc)3 Tb Dy(OAc)3 Ho(OAc)3 Er Tm Yb(OAc)3 Lu(OAc)3
Ac Th Pa UO2(OAc)2 Np Pu Am Cm Bk Cf Es