Editing Acetal (section)

==Examples==
===Sugars=== 
Since many sugars are polyhydroxy aldehydes and ketones, sugars are a rich source of acetals and ketals. Most [[glycosidic bond]]s in [[carbohydrate]]s and other [[polysaccharide]]s are acetal linkages.<ref>{{GoldBookRef|title=glycosides|file=G02661}}</ref> [[Cellulose]] is a ubiquitous example of a polyacetal.  

[[Benzylidene acetal]] and [[acetonide]] as protecting groups used in research of modified sugars.

===Chiral derivatives===
Acetals also find application as [[Chirality (chem)|chiral]] auxiliaries.  Indeed acetals of chiral glycols like, e.g. derivatives of tartaric acid can be asymmetrically opened with high selectivity.  This enables the construction of new chiral centers.<ref>P.J. Kocieński: ''Protecting Groups'', S.&nbsp;164–167.</ref>
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===Formaldehyde and acetaldehyde===
Formaldehyde forms a rich collection of acetals.  This tendency reflects the fact that low molecular weight aldehydes are prone to self-condensation such that the C=O bond is replaced by an acetal. The acetal formed from [[formaldehyde]] (two hydrogens attached to the central carbon) is sometimes called a ''formal''<ref>Morrison, Robert T. and Boyd, Robert N., "Organic Chemistry (6th ed)". p683. Prentice-Hall Inc (1992).</ref> or the [[methylenedioxy]] group. The acetal formed from [[acetone]] is sometimes called an [[acetonide]].  Formaldehyde forms [[Paraldehyde]] and [[1,3,5-Trioxane]]. [[Polyoxymethylene]] (POM) plastic, also known as "acetal" or "polyacetal", is a polyacetal (and a polyether), and a polymer of [[formaldehyde]]. [[Acetaldehyde]] converts to [[Metaldehyde]].

===Unusual acetals===
[[Phenylsulfonylethylidene]] (PSE) acetal is an example of arylsulfonyl acetal possessing atypical properties, like resistance to acid hydrolysis which leads to selective introduction and removal of the protective group.<ref name=":0">{{Cite journal|last=Chéry|first=Florence|last2=Rollin|first2=Patrick|last3=De Lucchi|first3=Ottorino|last4=Cossu|first4=Sergio|date=2000|title=Phenylsulfonylethylidene (PSE) acetals as atypical carbohydrate-protective groups|journal=Tetrahedron Letters|volume=41|issue=14|pages=2357–2360|doi=10.1016/s0040-4039(00)00199-4|issn=0040-4039}}</ref>

===Flavors and fragrances===
[[1,1-Diethoxyethane]] (acetaldehyde diethyl acetal), sometimes called simply "acetal", is an important flavouring compound in [[distilled beverage]]s.<ref>{{Cite book |last=Maarse |first=Henk |url=https://books.google.com/books?id=_OvXjhLUz-oC |title=Volatile Compounds in Foods and Beverages |date=1991-03-29 |publisher=CRC Press |isbn=978-0-8247-8390-7 |language=en}}</ref>  Two ketals of ethyl acetoacetate are used in commercial fragrances.<ref>{{cite book |doi=10.1002/14356007.t11_t02 |chapter=Flavors and Fragrances, 3. Aromatic and Heterocyclic Compounds |title=Ullmann's Encyclopedia of Industrial Chemistry |date=2016 |last1=Panten |first1=Johannes |last2=Surburg |first2=Horst |pages=1–45 |isbn=978-3-527-30673-2 }}</ref> [[Fructone]] ({{chem2|CH3C(O2C2H4)CH2CO2C2H5}}), an ethylene glycol ketal, and fraistone ({{chem2|CH3C(O2C2H3CH3)CH2CO2C2H5}}), a propylene glycol ketal, are commercial fragrances.