Lecture Notes: Carboxylic Acid Derivatives

Nomenclature and Properties

Acyl Halides (Acid Halides)

• Structure:
  • Composed of an acyl group and a halogen.
  • Derived from carboxylic acids.
• Naming:
  • Convert carboxylic acid name to acyl halide:
    • Acetic Acid (common name):
      • Drop the "-ic" and "acid", add "-yl" + halide.
      • Example: Acetyl chloride.
    • Ethanoic Acid (IUPAC name):
      • Same process as above.
      • Example: Ethanoyl chloride.
• Physical Properties:
  • Boiling point ~51°C.
  • Polar molecule due to oxygen and chlorine withdrawing electron density.
  • Interactions:
    • Dipole-Dipole Interactions: Stronger than London dispersion forces.
    • Higher boiling point than comparable two-carbon alkanes (e.g., ethane).
    • Lower boiling point than acetic acid due to lack of hydrogen bonding.
  • Solubility in Water:
    • Highly reactive with water; not considered soluble.

Acid Anhydrides

• Formation:
  • Derived from carboxylic acids by removing water.
  • Example: Two molecules of acetic acid form acetic anhydride.
• Naming:
  • Keep the acid name, drop "acid", and add "anhydride".
  • Examples:
    • Acetic anhydride (from acetic acid).
    • Ethanoic anhydride (from ethanoic acid).
    • Benzoic anhydride (from benzoic acid).
  • Mixed anhydrides:
    • Named by listing acids in alphabetical order + "anhydride".
    • Example: Acetic benzoic anhydride.
• Physical Properties:
  • Polarity:
    • Moderately polar due to carbonyl groups.
    • Dipole-dipole interactions and London dispersion forces present.
  • Boiling Point:
    • Example: Acetic anhydride ~140°C.
    • Lower than similar carboxylic acids (e.g., butanoic acid ~164°C) due to lack of hydrogen bonding.
  • Solubility in Water:
    • Reacts with water, not considered soluble.
• Reactivity:
  • Reacts with water but less reactive than acyl halides.

Conclusion

• Acyl halides and acid anhydrides are derived from carboxylic acids and have distinct nomenclature rules and physical properties.
• Reactivity with water affects their solubility, and intermolecular forces determine their boiling points.
• Future discussions will cover the reactivity of these derivatives in detail.