Acetal Definition in Chemistry

General structure of Acetals (Acetal and Ketal)

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An acetal is an organic molecule where two separate oxygen atoms are single bonded to a central carbon atom.
Acetals have the general structure of R2C(OR')2.
An older definition of acetal had one at least one R group as a derivative of an aldehyde where R = H, but an acetal can contain derivatives of ketones where neither R group is a hydrogen. This type of acetal is called a ketal.
Acetals that contain different R' groups are called mixed acetals.

Acetal Examples

Dimethoxymethane is an acetal compound.

Acetal is also a common name for the compound 1,1-diethoxyethane. The compound polyoxymethylene (POM) is a plastic that is also called simply "acetal" or "polyacetal."


  • IUPAC (1997). Compendium of Chemical Terminology (2nd ed.) (the "Gold Book"). "Ketals." doi:10.1351/goldbook.K03376
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Helmenstine, Anne Marie, Ph.D. "Acetal Definition in Chemistry." ThoughtCo, Aug. 28, 2020, Helmenstine, Anne Marie, Ph.D. (2020, August 28). Acetal Definition in Chemistry. Retrieved from Helmenstine, Anne Marie, Ph.D. "Acetal Definition in Chemistry." ThoughtCo. (accessed May 16, 2021).