Which one of the following reaction sequences is incorrect method to prepare phenol?

Solution to the Question: Which One of the Following Reaction Sequences is Incorrect Method to Prepare Phenol?

Option a: Aniline, NaNO₂ + HCl, H₂O, heating

Explanation: Aniline (C₆H₅NH₂) reacts with sodium nitrite (NaNO₂) and hydrochloric acid (HCl) to form a diazonium salt (C₆H₅N₂⁺Cl⁻). This diazonium salt can be hydrolyzed in water upon heating to give phenol (C₆H₅OH).

Conclusion: This is a valid method to prepare phenol. The reaction is correct.

Option b: Cumene, O₂, H₃O⁺

Explanation: This is the Cumene hydroperoxide process for the industrial preparation of phenol. Cumene (C₆H₅CH₂CH₃) reacts with oxygen (O₂) to form cumene hydroperoxide, which is then treated with acidic water (H₃O⁺) to yield phenol (C₆H₅OH) and acetone.

Conclusion: This is a valid method to prepare phenol. The reaction is correct.

Option c: NaOH, STP condition

Explanation: This is referring to the reduction of phenol using sodium hydroxide (NaOH) under standard temperature and pressure (STP). However, this reaction does not directly yield phenol. In fact, phenol is a starting material in many reactions rather than being produced by this method.

Conclusion: This is incorrect. This reaction does not prepare phenol and, thus, is the wrong method.

Option d: Oleum, NaOH, H₃O⁺

Explanation: In this reaction, oleum (a mixture of sulfur trioxide and sulfuric acid) reacts with sodium hydroxide (NaOH) to form sodium bisulfate. Further treatment with H₃O⁺ (acidic conditions) can yield phenol. This method is a valid way to prepare phenol.

Conclusion: This is a valid method to prepare phenol. The reaction is correct.

Final Answer:

The incorrect method to prepare phenol is Option c: NaOH, STP condition.