Question

Which of the following sets of reactants is used for the preparation of paracetamol from phenol?
(A) $HN{{O}_{3}},{{H}_{2}}/Pd,{{(C{{H}_{3}}CO)}_{2}}O$
(B) ${{H}_{2}}S{{O}_{4}},{{H}_{2}},Pd,{{(C{{H}_{3}}CO)}_{2}}O$
(C) ${{C}_{6}}{{H}_{5}}{{N}_{2}}Cl,SnC{{l}_{2}},{{(C{{H}_{3}}CO)}_{2}}O$
(D) $B{{r}_{2}}/{{H}_{2}}O,Zn/HCl,{{(C{{H}_{3}}CO)}_{2}}O$

Answer 1

Hint: Phenol undergoes nitration to form p-nitrophenol. p-nitrophenol undergoes reduction then acetylation to form paracetamol, Nitric acid is used to add nitro groups on phenol. Acetic anhydride adds an acetylation group.

Complete step by step solution:
In paracetamol, para indicates acetyl group is present at para position with respect to a hydroxyl group and ol at the end indicates hydroxyl group.
The IUPAC name of Paracetamol is N-(4-hydroxyphenyl)ethanamide.
Sulphuric acid is used in sulphonation reactions. Zinc and hydrochloric acid, tin chloride and Hydrogen palladium are reducing agents and are used in reduction reactions.
Acetic anhydride is used as acetylating agent, it replaces a hydrogen atom with an acetyl group.
Hydroxyl group in phenol is ortho and para directing. When nitric acid is added to phenol, phenol undergoes nitration to form o-Nitrophenol and p-Nitrophenol, p-Nitrophenol is a major product.

P-nitrophenol undergoes reduction to form 4-Aminophenol. Hydrogen is added in presence of palladium, which acts as a reducing agent and nitro group is reduced to Amino group.

p-Aminophenol undergoes acetylation to form paracetamol. Acetic anhydride is an acetylating agent, Hydrogen atom of an amino group is replaced by acetyl group and paracetamol is produced.


Hence, option (A) is the correct anser.

Note: Hydroxyl group in phenol is ortho and para directing. p-Nitrophenol is a major product. and the Nitro group is reduced to an Amino group. The amino group undergoes acetylation to form paracetamol. Nitric acid is used in nitration of phenol.