Reactions at the $\alpha$ carbon

• Aldol addition: The formation of $\beta$ Đhydroxy aldehydes or ketones when an enolate reacts with an $\alpha$-carbon of another carbonyl (Note: this can occur in the presence of a base or an acid). See Figure 47.15 below.

  Figure 47.15: Aldol addition.

  

• Aldol condensation: The formation of a conjugated system in aldehydes or ketones (Note: this can occur in the presence of a base or an acid). See Figure 47.16 below.

  Figure 47.16: Aldol condensation.

  

• Haloform reactions: Reaction of a methyl ketone with halogens (in the presence of a base) which produces a methyl group with multiple halogens. See Figure 47.17 below.

  Figure 47.17: Haloform reactions.

  

• Oxidation
  • Aldehydes are easier to oxidize than ketones
  • Common, strong oxidizing agents include potassium permanganate (KMnO$_{4}$), lithium aluminum hydride (LAH), sodium borohydride (NaBH$_{4}$) or silver oxide (AgO):
    

    Figure 47.18: Aldehyde oxidation.