ketones are named as substituents, use either the prefix oxo– or keto–. Figure 6.3 shows some
examples of ketones.
Figure 6.3. Naming KetonesPHYSICAL PROPERTIES
The physical properties of aldehydes and ketones are governed by the presence of the carbonyl
group. The dipole of the carbonyl is stronger than the dipole of an alcohol because the double-
bonded oxygen is more electron-withdrawing than the single bond to oxygen in the hydroxyl group.
In solution, the dipole moments associated with these polar carbonyl groups increase
intermolecular attractions, causing an elevation in boiling point relative to their parent alkanes.
However, even though aldehydes and ketones have dipoles more polar than those of alcohols, the
elevation in boiling point is less than that in alcohols because no hydrogen bonding is present. In
reactions, aldehydes and ketones both act as electrophiles, making good targets for nucleophiles.
This is due to the electron-withdrawing properties of the carbonyl oxygen, which leaves a partial
positive charge on the carbon, as shown in Figure 6.4. Generally, aldehydes are more reactive
toward nucleophiles than ketones because they have less steric hindrance and fewer electron-
donating alkyl groups.
Figure 6.4. Polarity of the Carbonyl Group