Figure 1.7. Naming Aldehydes
The carbonyl group of the aldehyde usually does not receive a number in the name because it is a
terminal functional group.Methanal, ethanal, and propanal are referred to almost exclusively by their common names,
formaldehyde, acetaldehyde, and propionaldehyde, rather than their IUPAC names. These
molecules are shown in Figure 1.8.
Figure 1.8. Common Names of AldehydesKETONES
Ketones contain a carbonyl group somewhere in the middle of the carbon chain. Because this is the
case, we will always have to assign a number to the carbonyl carbon when naming ketones (except
propanone, which must have the ketone on carbon 2 by default). Ketones are named by replacing
- e in the name of the parent alkane with the suffix –one. Just as when naming other compounds, be
sure to give the carbonyl the lowest possible number if it is the highest-priority group.
BRIDGE
Sugars are classified as either aldoses (aldehyde sugars) or ketoses (ketone sugars).
Understanding nomenclature can help you to identify the structure of a sugar as well as
some of its physical properties. Carbohydrate structure is discussed in Chapter 4 of MCAT
Biochemistry Review.