Producing Phenol (Cambridge (CIE) A Level Chemistry): Revision Note

Production of Phenol

• Phenols are organic compounds characterised by the presence of an -OH group which is attached to a benzene ring

• Phenols can be produced by the reaction of phenylamine with nitrous acid (HNO₂)

Production of phenol

• Phenols can be prepared from phenylamines under the following reaction conditions:

  • NaNO₂ with dilute acid (to form HNO₂)

  • Ice to keep the temperature below 10 ^oC (step 1)

  • Heat (step 3)

• This reaction involves three steps:

  • Step 1 - The HNO₂ is so unstable that it needs to be prepared in a test-tube by reacting sodium nitrite (NaNO₂) and dilute hydrochloric acid (HCl) while keeping the temperature below 10 ^oC using ice

Forming nitrous acid, HNO₂

Nitrous acid can be prepared in a test-tube by reacting sodium nitrate with dilute hydrochloric acid

• Step 2 - Phenyl amine is then reacted with the HNO₂ to form an unstable diazonium salt

Forming benzenediazonium chloride 

Benzenediazonium chloride is an unstable diazonium salt

• Step 3 - The diazonium salt is so unstable that it will thermally decompose when heated to form a phenol

Forming phenol 

Phenol is formed by the thermal decomposition of the unstable diazonium salt, benzenediazonium chloride