Sugars Since many sugars are polyhydroxy aldehydes and ketones, sugars are a rich source of acetals and ketals. Most
glycosidic bonds in
carbohydrates and other
polysaccharides are acetal linkages.
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
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.
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 or the
methylenedioxy group. The acetal formed from
acetone is sometimes called an
acetonide. Formaldehyde forms
paraformaldehyde 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
paraldehyde and
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.
Flavors and fragrances 1,1-Diethoxyethane (acetaldehyde diethyl acetal), sometimes called simply "acetal", is an important flavouring compound in
distilled beverages. Two ketals of ethyl acetoacetate are used in commercial fragrances.
Fructone (), an ethylene glycol ketal, and fraistone (), a propylene glycol ketal, are commercial fragrances. ==Related compounds==