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In
H2C=C=O + CH3COOH -> (CH3CO)2O
This reagent is common in the laboratory; its use cogenerates acetic acid.
Acetylations can also be achieved using less electrophilic reagents, such as esters of thioacetic acid.
In organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clayden, J ...
, acetylation is an organic esterification reaction with acetic acid. It introduces an acetyl group
In organic chemistry, acetyl is a functional group with the chemical formula and the structure . It is sometimes represented by the symbol Ac (not to be confused with the element actinium). In IUPAC nomenclature, acetyl is called ethanoyl, ...
into a chemical compound
A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...
. Such compounds are termed ''acetate ester
In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ...
s'' or simply '' acetates''. Deacetylation is the opposite reaction, the removal of an acetyl group from a chemical compound.
Organic synthesis
Acetate esters andacetamide
Acetamide (systematic name: ethanamide) is an organic compound with the formula CH3CONH2. It is the simplest amide derived from acetic acid. It finds some use as a plasticizer and as an industrial solvent. The related compound ''N'',''N''-dime ...
s are generally prepared by acetylations. Acetylations are often used in making C-acetyl bonds in Friedel-Crafts reactions. Carbanions and their equivalents are susceptible to acetylations.
Acetylation reagents
Many acetylations are achieved using these three reagents: * Acetic anhydride. This reagent is common in the laboratory; its use cogenerates acetic acid. * Acetyl chloride. This reagent is also common in the laboratory, but its use cogenerates hydrogen chloride, which can be undesirable. * Ketene. At one time acetic anhydride was prepared by the reaction of ketene with acetic acid: :Acetylation of cellulose
Cellulose is a polyol and thus susceptible to acetylation, which is achieved using acetic anhydride. Acetylation disrupts hydrogen bonding, which otherwise dominates the properties of cellulose. Consequently, the cellulose esters are soluble in organic solvents and can be cast into fibers and films.Acetylation/deacetylation in biology
Acetylation is one type ofpost-translational modification
Post-translational modification (PTM) is the covalent and generally enzymatic modification of proteins following protein biosynthesis. This process occurs in the endoplasmic reticulum and the golgi apparatus. Proteins are synthesized by ribo ...
of proteins. The acetylation of the ε-amino group of lysine, which is common, converts a charged side chain to a neutral one. Acetylation/deacetylation of histones also plays a role in gene expression and cancer
Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...
. These modifications are effected by enzymes called histone acetyltransferase
Histone acetyltransferases (HATs) are enzymes that acetylate conserved lysine amino acids on histone proteins by transferring an acetyl group from acetyl-CoA to form ε-''N''-acetyllysine. DNA is wrapped around histones, and, by transferring an ...
s (HATs) and histone deacetylases (HDACs).
See also
* Acetoxy group * Acylation *Amide
In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a compound with the general formula , where R, R', and R″ represent organic groups or hydrogen atoms. The amide group is called a peptide bond when it i ...
*Ester
In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ...
*Organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one o ...
References
{{Reflist, 35em Organic reactions