General Properties of Carboxylic Acids

 1. Dissociation in Water  

- Carboxylic acids dissociate in water, releasing hydrogen ions (H⁺).  

- This gives them their characteristic acidic behavior.  

2. Effect of Alkyl Group Size  

- As the number of carbon atoms in the alkyl (R) group increases:  

  - Solubility decreases (larger molecules are less soluble in water).  

  - Acidity decreases (e.g., propanoic acid is less acidic than ethanoic acid).  

- Reason: More electrons are transferred from the alkyl group to the O–H bond, strengthening it and making it less likely to release H⁺ ions.  

3. Odour  

- Carboxylic acids often have strong, pungent odours, especially those that are volatile.  

4. Physical State  

- Lower carboxylic acids (e.g., methanoic and ethanoic acids) are colourless liquids at room temperature.  

5. Boiling Points  

- Carboxylic acids have much higher boiling points compared to corresponding alkanes.  

- Reason: Strong hydrogen bonding between molecules.  

6. Stability  

- Carboxylic acids are fairly stable compounds.  

- They are not easily decomposed by heat or affected by ordinary oxidizing, reducing, or dehydrating agents.  

Oxidation of Carboxylic Acids  

- Carboxylic acids are themselves products of oxidation.  

- Example pathway:  

  - Primary alkanols → Alkanals → Alkanoic acids.  

- Some carboxylic acids (e.g., formic acid and ethanedioic acid) can be further oxidized to carbon(IV) oxide (CO₂), releasing hydrogen.