Ethanoic Acid (CH₃COOH)

- Ethanoic acid is the acid present in vinegar.    

- The complete oxidation of ethanol can prepare it.  

Preparation of Ethanoic Acid  

Oxidation of Ethanol (Reflux Method):  

- Ethanol is oxidised using acidified sodium or potassium dichromate (with concentrated H₂SO₄).  

- Ethanol is added dropwise into the excess acidified dichromate solution using a dropping funnel.  

- The reaction occurs in two stages:  

  1. Ethanol is partially oxidised to ethanal.  

  2. Ethanal is further oxidised to ethanoic acid.  

Other Methods:  

- Distilling anhydrous sodium ethanoate with concentrated sulphuric acid.  

- Boiling methyl cyanide with an acid.  

Important Notes:  

- Use a glass apparatus because hot acid vapour attacks corks and rubber.  

- H₂SO₄ is used instead of HCl, since HCl is too volatile.  

Physical Properties of Ethanoic Acid  

- Solubility: Very soluble in water.  

- Acidity: Turns blue litmus red; dilute solutions taste sour.  

- Boiling Point: 118 °C.  

- Glacial Ethanoic Acid: Pure, anhydrous form; freezes below 17 °C into ice‑like crystals.  

- Appearance: Colourless liquid with a sharp, pungent smell.