Aldehydes are organic compounds containing the RCHO functional group where R can be hydrogen or another carbon-containing moiety. Aldehydes are named after the corresponding carboxylic acids by dropping the -ic or -oic suffix and adding -aldehyde or -al (e.g., acetic acid acetaldehyde, ethanoic acid → ethanal), or if derived from acyclic aliphatic hydrocarbons, by dropping the final e and adding -al (e.g., propane → propanal). Formyl derivatives of ring compounds may be called carbaldehydes as in cyclopentanecarbaldehyde. See the IUPAC rules for more complex cases.
Aldehydes can be reduced to alcohols or oxidized to carboxylic acids and undergo a variety of addition and condensation reactions, for example, addition of cyanide in the cyanohydrin synthesis, or condensation with another aldehyde in a benzoin reaction or condensation with the carbon adjacent to an aldehyde or ketone in the aldol reaction.
The name may be derived from the phrase “alcohol dehydrogenatum.”