Aldehydes and Ketones Chapter 4

Aldehydes and Ketones

• Aldehydes have at least one hydrogen attached to the carbonyl group, while ketones have two carbons attached to the carbonyl group.

Naming Aldehydes

• Find the longest carbon chain that contains the aldehyde group.
• Change the ending of the root hydrocarbon name by dropping –e and adding –al.
• Number the longest carbon chain so the C=O group has the lowest number.
• All other branches and groups are named and located using standard IUPAC system.

Naming Ketones

• Find the longest chain that contains C=O.
• Using the root alkane name, drop the –e ending and change to –one.
• Number the longest carbon chain so the C=O group has the lowest number.
• Name and number other substituents as before.

Important Aldehydes and Ketones

• Formaldehyde: a gas at room temperature, used as a sterilizer, embalming fluid, and starting material for plastics such as Formica and Bakelite.
• Acetone (propanone): an important organic solvent, used in nail polish remover, and miscible with water.
• Progesterone and Testosterone: female and male sex hormones, respectively, which are ketones.
• Some aldehydes and ketones are used in flavorings, such as Vanillin (vanilla), Cinnamaldehyde (cinnamon), Citral (citrus flavoring), and Camphor (medicinal odor).

Physical Properties of Aldehydes and Ketones

• The carbonyl group is moderately polar, but it cannot hydrogen bond between molecules.
• The polarity of the C=O group allows for interactions, but the attraction is not as strong as hydrogen bonding.
• The boiling point of aldehydes and ketones is higher than alkanes, but lower than alcohols.
• Low molecular weight aldehydes and ketones are water-soluble due to hydrogen bonding with water molecules.

Reactions of Aldehydes and Ketones

• Oxidation: aldehydes and ketones can be oxidized to produce other compounds.
• The difference in reactivity toward oxidation is the chief reason why aldehydes and ketones are classified in separate families.
• Hydrogenation: aldehydes and ketones can be reduced to alcohols by the addition of H2 in the presence of catalysts.