Editing Acetic anhydride (section)

==Reactions==
Acetic anhydride is a versatile reagent for [[acetylation]]s, the introduction of acetyl groups to organic substrates.<ref>{{citation | title = Acid Anhydrides | url = http://www.chemguide.co.uk/organicprops/anhydridemenu.html | work = Understanding Chemistry | access-date = 2006-03-25}}.</ref> In these conversions, acetic anhydride is viewed as a source of {{chem2|CH3CO+}}.

===Acetylation of alcohols, amines, aromatics===
[[Alcohol (chemistry)|Alcohol]]s and [[amine]]s are readily acetylated.<ref>{{citation | first = Bassam Z. | last = Shakhashiri | title = Acetic Acid & Acetic Anhydride | url = http://scifun.chem.wisc.edu/CHEMWEEK/AceticAcid/AceticAcid.html | work = Science is Fun… | publisher = Department of Chemistry, University of Wisconsin | access-date = 2006-03-25 | archive-url = https://web.archive.org/web/20060303081507/http://scifun.chem.wisc.edu/chemweek/AceticAcid/AceticAcid.html | archive-date = 2006-03-03 | url-status = dead }}.</ref> For example, the reaction of acetic anhydride with [[ethanol]] yields [[ethyl acetate]]:
:{{chem2|(CH3CO)2O + CH3CH2OH -> CH3CO2CH2CH3 + CH3COOH}}
Often a base such as [[pyridine]] is added to function as catalyst. In specialized applications, [[Lewis acid]]ic [[scandium]] salts have also proven effective catalysts.<ref>{{OrgSynth | last1 = Macor | first1 = John | last2 = Sampognaro | first2 = Anthony J. | last3 = Verhoest | first3 = Patrick R. | last4 = Mack | first4 = Robert A. | title = (''R'')-(+)-2-Hydroxy-1,2,2-Triphenylethyl Acetate | prep = V77P0045 | year = 2000 | volume = 77 | pages = 45 | collvol = 10 | collvolpages = 464 | doi = 10.15227/orgsyn.077.0045 }}</ref>

Aromatic rings are acetylated by acetic anhydride.  Usually acid catalysts are used to accelerate the reaction. Illustrative are the conversions of [[benzene]] to [[acetophenone]]<ref>Roger Adams and C. R. Noller "p-Bromoacetophenone" Org. Synth. 1925, vol. 5, p. 17. {{doi|10.15227/orgsyn.005.0017}}</ref> and [[ferrocene]] to acetylferrocene:<ref>{{citation | last = Taber | first = Douglass F. | title = Column chromatography: Preparation of Acetyl Ferrocene | url = http://valhalla.chem.udel.edu/ferroc.html | publisher = Department of Chemistry and Biochemistry, University of Delaware | access-date = 2009-08-27 | archive-url = https://web.archive.org/web/20090502011406/http://valhalla.chem.udel.edu/ferroc.html | archive-date = 2009-05-02 | url-status = dead }}.</ref>
:{{chem2|(C5H5)2Fe  +  (CH3CO)2O   ->   (C5H5)Fe(C5H4COCH3)  +  CH3CO2H}}

===Preparation of other acid anhydrides===
Dicarboxylic acids are converted to the anhydrides upon treatment with acetic anhydride.<ref>B. H. Nicolet and J. A. Bender "3-Nitrophthalic Anhydride" Org. Synth. 1927, vol. 7, 74.
{{doi|10.15227/orgsyn.007.0074}}</ref>  It is also used for the preparation of mixed anhydrides such as that with nitric acid, [[acetyl nitrate]].

===Precursor to geminal diacetates===
[[Aldehyde]]s react with acetic anhydride in the presence of an acidic [[catalyst]] to give geminal diacetates.<ref>R. T. Bertz "Furfuryl Diacetate" Org. Synth. 1953, 33, 39. {{doi|10.15227/orgsyn.033.0039}}</ref>  A former industrial route to [[vinyl acetate]] involved the intermediate [[ethylidene diacetate]], the geminal diacetate obtained from [[acetaldehyde]] and acetic anhydride:<ref>G. Roscher "Vinyl Esters" in ''Ullmann's Encyclopedia of Chemical Technology'', 2007 John Wiley & Sons: New York. {{doi|10.1002/14356007.a27_419}}</ref>
:{{chem2|CH3CHO  +  (CH3CO)2O   ->   (CH3CO2)2CHCH3}}

===Hydrolysis===
Acetic anhydride dissolves in water to approximately 2.6% by weight.<ref>{{citation|title=Acetic Anhydride: Frequently Asked Questions |url=http://www.bp.com/liveassets/bp_internet/globalbp/STAGING/global_assets/downloads/pdfs/acetyls_aromatics_pta/AceticAnhydrideFAQ.pdf |publisher=British Petroleum |access-date=2006-05-03 |url-status=dead |archive-url=https://web.archive.org/web/20071011104749/http://www.bp.com/liveassets/bp_internet/globalbp/STAGING/global_assets/downloads/pdfs/acetyls_aromatics_pta/AceticAnhydrideFAQ.pdf |archive-date=2007-10-11 }}.</ref> Aqueous solutions have limited stability because, like most acid anhydrides, acetic anhydride hydrolyses to give carboxylic acids. In this case, acetic acid is formed, this reaction product being fully water miscible:<ref>{{citation|title=Acetic Anhydride: Material Safety Data Sheet (PDF) |url=http://www.celanese.com/msds/pdf/570-22027587.pdf |publisher=Celanese |access-date=2006-05-03 |url-status=dead |archive-url=https://web.archive.org/web/20070927025258/http://www.celanese.com/msds/pdf/570-22027587.pdf |archive-date=2007-09-27 }}.</ref>
:{{chem2|(CH3CO)2O + H2O -> 2 CH3COOH}}

===Enolate formation===
Acetic anhydride forms the enolate in the presence of [[acetate]] as base.  The enolate can be [[chemical trap|trapped]] by condenation with [[benzaldehyde]].  In the 19th century, this chemistry,  the [[Perkin reaction]], was used for the production of [[cinnamic acid]]:<ref>{{Cite book |last=Lassar-Cohn |first=Dr |url=https://books.google.com/books?id=KxhIAAAAIAAJ&pg=PA104 |title=A Laboratory Manual of Organic Chemistry: A Compendium of Laboratory Methods for the Use of Chemists, Physicians, and Pharmacists |last2=Smith |first2=Alexander |date=1895 |publisher=Macmillian and Company Limited |language=en}}</ref>
:{{chem2|(CH3CO)2O  +  C6H5CHO  ->  C6H5CH\dCHCO2H  +  CH3CO2H}}

===Lewis base properties===
The carbonyl groups in acetic anhydride are weakly basic.  A number of adducts are known, such as the derivative of [[titanium tetrachloride]], TiCl<sub>4</sub>((CH<sub>3</sub>CO)<sub>2</sub>O).<ref>{{cite journal|author=B. Viard, M. Poulain, D. Grandjean, J. Amaudrut|journal=J. Chem. Res.|volume=84|year=1983|page=853}}</ref>