Aldehydes, Ketones & Carboxylic Acids

• Cyclic compounds containing carbonyl group

• Aldehydes: Carbonyl group at terminal carbon

• Ketones: Carbonyl group at any other carbon

• Carboxylic acids: Carbonyl and hydroxyl groups on adjacent carbon

• Examples:

  • Aldehyde: Formaldehyde (HCHO)
  • Ketone: Acetone (CH₃COCH₃)
  • Carboxylic acid: Acetic acid (CH₃COOH)

• IUPAC nomenclature used for naming these compounds

Aldehydes, Ketones & Carboxylic Acids

IUPAC names of cyclic aldehydes

• Cyclic aldehydes have a carbonyl group bonded to a carbon atom within the ring structure.
• The IUPAC name for such aldehydes follows a specific set of rules.
• The ring carbon atom next to the carbonyl group is assigned as the number 1 carbon.
• The suffix “-al” is used to indicate the presence of the aldehyde group. Example: Cyclohexanecarbaldehyde

IUPAC names of cyclic ketones

• Cyclic ketones contain a carbonyl group bonded to a carbon atom within the ring structure.
• The IUPAC name for cyclic ketones also has a specific set of rules.
• The carbon atom next to the carbonyl group is assigned as the number 1 carbon.
• The suffix “-one” is used to indicate the presence of the ketone group. Example: Cyclopentanone

IUPAC names of carboxylic acids

• Carboxylic acids have both a carbonyl group and a hydroxyl group on adjacent carbon atoms.
• The IUPAC name for carboxylic acids is derived from the corresponding alkane by replacing the “-e” ending with “-oic acid”.
• The carbon atom of the carbonyl group is assigned as the number 1 carbon.
• The carboxyl group is always given the highest priority in numbering the carbon atoms. Example: Ethanoic acid (acetic acid)

Common names of aldehydes and ketones

• Some aldehydes and ketones have common names that are widely used.
• Formaldehyde is the common name for methanal (HCHO).
• Acetone is the common name for propanone (CH₃COCH₃).
• Common names are often used for compounds with simple and well-known structures.

Physical properties of aldehydes and ketones

• Aldehydes and ketones have higher boiling points than alkanes or alkenes of comparable molecular weight.
• This is due to the presence of the highly polar carbonyl group, which allows for stronger intermolecular forces.
• Ketones generally have higher boiling points compared to aldehydes of similar molecular weight.

Solubility of aldehydes and ketones

• Aldehydes and ketones with smaller molecular weights are soluble in water.
• Solubility decreases as the size of the hydrocarbon chain increases.
• Aldehydes and ketones can form hydrogen bonds with water molecules through the carbonyl group.

Chemical reactions of aldehydes and ketones

• Aldehydes and ketones undergo a variety of chemical reactions due to the presence of the carbonyl group.
• Some important reactions include:
  • Nucleophilic addition reactions
  • Oxidation reactions
  • Reduction reactions
  • Condensation reactions

Nucleophilic addition reactions

• Aldehydes and ketones can undergo nucleophilic addition reactions.
• The carbonyl carbon is attacked by a nucleophile, leading to the addition of a new group.
• The nucleophile can be a negatively charged ion or a molecule with a lone pair of electrons. Example: Addition of sodium cyanide to propanal leads to the formation of 2-hydroxy-2-methylpropanenitrile.

Oxidation reactions of aldehydes and ketones

• Aldehydes can be easily oxidized to carboxylic acids using mild oxidizing agents such as Tollens’ reagent or Fehling’s solution.
• Ketones, however, are not easily oxidized under normal conditions.
• They require stronger oxidizing agents, such as concentrated nitric acid or potassium permanganate, to form carboxylic acids.

Reduction reactions of aldehydes and ketones

• Aldehydes and ketones can be reduced to alcohols using reducing agents such as sodium borohydride (NaBH₄) or lithium aluminum hydride (LiAlH₄).
• The carbonyl group is converted to a hydroxyl group during the reduction reaction.
• Aldehydes are typically more reactive towards reduction than ketones.

Aldehydes, Ketones & Carboxylic Acids

IUPAC names of cyclic aldehydes

• Cyclic aldehydes have a carbonyl group bonded to a carbon atom within the ring structure.
• The IUPAC name for such aldehydes follows a specific set of rules.
• The ring carbon atom next to the carbonyl group is assigned as the number 1 carbon.
• The suffix “-al” is used to indicate the presence of the aldehyde group. Example: Cyclohexanecarbaldehyde

IUPAC names of cyclic ketones

• Cyclic ketones contain a carbonyl group bonded to a carbon atom within the ring structure.
• The IUPAC name for cyclic ketones also has a specific set of rules.
• The carbon atom next to the carbonyl group is assigned as the number 1 carbon.
• The suffix “-one” is used to indicate the presence of the ketone group. Example: Cyclopentanone

IUPAC names of carboxylic acids

• Carboxylic acids have both a carbonyl group and a hydroxyl group on adjacent carbon atoms.
• The IUPAC name for carboxylic acids is derived from the corresponding alkane by replacing the “-e” ending with “-oic acid”.
• The carbon atom of the carbonyl group is assigned as the number 1 carbon.
• The carboxyl group is always given the highest priority in numbering the carbon atoms. Example: Ethanoic acid (acetic acid)

Common names of aldehydes and ketones

• Some aldehydes and ketones have common names that are widely used.
• Formaldehyde is the common name for methanal (HCHO).
• Acetone is the common name for propanone (CH₃COCH₃).
• Common names are often used for compounds with simple and well-known structures.

Physical properties of aldehydes and ketones

• Aldehydes and ketones have higher boiling points than alkanes or alkenes of comparable molecular weight.
• This is due to the presence of the highly polar carbonyl group, which allows for stronger intermolecular forces.
• Ketones generally have higher boiling points compared to aldehydes of similar molecular weight.

Solubility of aldehydes and ketones

• Aldehydes and ketones with smaller molecular weights are soluble in water.
• Solubility decreases as the size of the hydrocarbon chain increases.
• Aldehydes and ketones can form hydrogen bonds with water molecules through the carbonyl group.

Chemical reactions of aldehydes and ketones

• Aldehydes and ketones undergo a variety of chemical reactions due to the presence of the carbonyl group.
• Some important reactions include:
  • Nucleophilic addition reactions
  • Oxidation reactions
  • Reduction reactions
  • Condensation reactions

Nucleophilic addition reactions

• Aldehydes and ketones can undergo nucleophilic addition reactions.
• The carbonyl carbon is attacked by a nucleophile, leading to the addition of a new group.
• The nucleophile can be a negatively charged ion or a molecule with a lone pair of electrons. Example: Addition of sodium cyanide to propanal leads to the formation of 2-hydroxy-2-methylpropanenitrile.

Oxidation reactions of aldehydes and ketones

• Aldehydes can be easily oxidized to carboxylic acids using mild oxidizing agents such as Tollens’ reagent or Fehling’s solution.
• Ketones, however, are not easily oxidized under normal conditions.
• They require stronger oxidizing agents, such as concentrated nitric acid or potassium permanganate, to form carboxylic acids.

Reduction reactions of aldehydes and ketones

• Aldehydes and ketones can be reduced to alcohols using reducing agents such as sodium borohydride (NaBH₄) or lithium aluminum hydride (LiAlH₄).
• The carbonyl group is converted to a hydroxyl group during the reduction reaction.
• Aldehydes are typically more reactive towards reduction than ketones.