The middle structure is an intermediate structure; since two hydroxyl groups
do not stay attached to the same carbon, it changes to the aldehyde by a water
molecule “breaking away.”
The aldehyde name is derived from the alcohol name by dropping the -ol and
adding -al.
Ethanol forms ethanal (acetaldehyde) in the same manner.
Organic Acids or Carboxylic Acids
The functional group of an organic acid is the carboxyl group. The
general formula is R—COOH.
TIP
The carboxyl group is the functional group of an organic acid. It isPREPARATION FROM AN ALDEHYDE. Organic acids can be prepared by the mild
oxidation of an aldehyde. The simplest acid is methanoic acid, which is present in
ants, bees, and other insects. A typical reaction is:
Notice that in the IUPAC system the name is derived from the alkane stem by
adding -oic.
Ethanal can be oxidized to ethanoic acid: