Aldehydes and Ketones

Nomenclature

• Aldehydes: characterized by the -CHO group.

• Ketones: characterized by the C=O group bonded to two carbon atoms.

Preparation

• From primary alcohols: Oxidation of primary alcohols using oxidizing agents such as potassium dichromate (K2Cr2O7) or pyridinium chlorochromate (PCC)

• From secondary alcohols: Oxidation of secondary alcohols with stronger oxidizing agents such as Jones reagent (a mixture of chromic acid and sulfuric acid) or potassium permanganate (KMnO4).

• By oxidation of alkenes: Alkenes can be oxidized to form aldehydes or ketones using reagents such as ozone (O3), potassium permanganate (KMnO4), or peroxyacids.

Reactions

• Nucleophilic addition reactions

  • Addition of HCN: Aldehydes and ketones react with hydrogen cyanide (HCN) to form cyanohydrins.
  • Addition of NH3: Aldehydes and ketones react with ammonia (NH3) to form imines.
  • Addition of Grignard reagents: Aldehydes and ketones react with Grignard reagents (R-MgX) to form alcohols.
  • Addition of organolithium reagents: Aldehydes and ketones react with organolithium reagents (R-Li) to form alcohols.

• Oxidation reactions

  • To carboxylic acids: Aldehydes are easily oxidized to carboxylic acids using oxidizing agents such as potassium permanganate (KMnO4), potassium dichromate (K2Cr2O7), or nitric acid (HNO3).

• Ketones are also oxidized to carboxylic acids but under harsher conditions and with stronger oxidizing agents.

• Reduction reactions

• To primary alcohols: Both aldehydes and ketones can be reduced to primary alcohols using reducing agents such as sodium borohydride (NaBH4) or lithium aluminum hydride (LiAlH4).

• To secondary alcohols: Ketones can be reduced to secondary alcohols using milder reducing agents such as isopropanol and aluminum isopropoxide.

Carboxylic Acids

Nomenclature

• Carboxylic acids are characterized by the -COOH group.

Preparation

• From primary alcohols: Oxidation of primary alcohols using oxidizing agents such as potassium permanganate (KMnO4), potassium dichromate (K2Cr2O7), or nitric acid (HNO3).

• From secondary alcohols: Oxidation of secondary alcohols with stronger oxidizing agents such as Jones reagent (a mixture of chromic acid and sulfuric acid).

• By oxidation of aldehydes and ketones: Aldehydes are easily oxidized to carboxylic acids using oxidizing agents such as potassium permanganate (KMnO4), potassium dichromate (K2Cr2O7), or nitric acid (HNO3).

Ketones are also oxidized to carboxylic acids but under harsher conditions and with stronger oxidizing agents.

Reactions

• Nucleophilic substitution reactions

  • Esterification: Reaction with alcohols in the presence of an acid catalyst to form esters.
  • Amidification: Reaction with ammonia or amines to form amides.

• Reduction reactions

  • To primary alcohols: Carboxylic acids can be reduced to primary alcohols using reducing agents such as lithium aluminum hydride (LiAlH4) or borane (BH3).
  • To secondary alcohols: Carboxylic acids with two or more carbon atoms can be reduced to secondary alcohols using milder reducing agents such as isopropanol and aluminum isopropoxide.