Lecture on Aldehydes and Ketones

Formation and Oxidation

• Aldehydes and ketones are formed by the oxidation of alcohols.
• Organic chemistry involves oxidizing hydrocarbons to alcohols, then to aldehydes or ketones, acids, and possibly carbon dioxide.

Naming Conventions

• Aldehydes: Add 'al' to the parent hydrocarbon name (e.g., butanal).
• Ketones: Add 'one' to the parent hydrocarbon name (e.g., butanone).

Reactions

Nucleophilic Addition Reactions

• Hydrate Formation:

  • Aldehydes in acidified water undergo protonation of the carbonyl oxygen followed by nucleophilic attack on the carbonyl carbon.
  • Leads to the formation of a geminal diol (hydrate).

• Hemiacetal and Acetal Formation:

  • Aldehydes and ketones react with alcohols instead of water.
  • Protonation of the carbonyl oxygen primes for nucleophilic attack by alcohol.
  • If only one 'OR' group forms, it's a hemiacetal; two 'OR' groups form an acetal.

• Imine and Enamine Formation:

  • Reaction of ketones with ammonia (NH3) leads to imine formation.
  • Imines can tautomerize to form enamines.

• Tautomerization:

  • Keto-enol tautomerism involves converting an enol form to a keto form, often facilitated by base.
  • Similarly, imine-enamine tautomerism occurs.

Biological Relevance

• Phosphoenolpyruvate (PEP) and ATP Formation:
  • PEP converts to pyruvate in glycolysis, where enol to keto tautomerism provides energy to synthesize ATP.

Carbohydrates

• Glucose can form cyclic hemiacetals in aqueous solutions, shifting between linear and ring forms rapidly.

Additional Topics

• Oxidation and Reduction:
  • Oxidation of aldehydes forms carboxylic acids.
  • Reduction of ketones typically uses lithium aluminum hydride or NaBH4.

Key Concepts and Philosophical Interlude

• Discussion on perception and the philosophical question of reality.

• Philosophical note on the perception of color and reality—consensus on linguistic definitions lacking factual basis.

Preview of Next Topics

• Focus on enolates and anions leading to the aldol reaction and Claisen reaction.
• Brief coverage on nitrogen-containing compounds and spectroscopy.

Conclusion

• Emphasis on revisiting lab techniques in the practical phase of learning.