60. Carboxylic Acids

1. What are Carboxylic Acids?

Carboxylic acids are a homologous series of organic compounds. They are identified by their functional group, which is COOH.

  • Naming: Their names always end in -anoic acid.

  • The first four in the series are:

    • Methanoic acid: HCOOH

    • Ethanoic acid: CH3COOH

    • Propanoic acid: C2H5COOH

    • Butanoic acid: C3H7COOH

  • Formula Tip: When writing these formulas, the COOH group should always be kept together at the end.

2. Acidic Properties

As the name suggests, these compounds are acids and behave like other acids, but with some specific differences:

  • Weak Acids: Carboxylic acids are weak acids, meaning they do not fully ionize in water. Not all the molecules release their hydrogen ions (H+).

  • Ionization Equations: Because the reaction is reversible, an equilibrium arrow is used between the full acid and the ionized version.

  • Ion Naming: When they ionize, the negative ions formed have names ending in -anoate. For example, propanoic acid ionizes into a propanoate ion and a hydrogen ion.

3. Reactions with Metal Carbonates

Like other acids, carboxylic acids react with metal carbonates to form three products:

  • General Equation: Carboxylic acid + Metal carbonate —→ Salt + Water + Carbon dioxide

  • Example: Ethanoic acid + Potassium carbonate —→ Potassium ethanoate + Water + Carbon dioxide.

4. How Carboxylic Acids are Made

Carboxylic acids are produced through the oxidation of alcohols.

  • Process: An alcohol (e.g., butanol) is reacted with an oxidizing agent.

  • Result: The oxidizing agent adds oxygen to the molecule, converting the alcohol into its corresponding carboxylic acid (e.g., butanoic acid). The number of carbon atoms remains the same.