Question

Write the reactions for the action of following reagents on phenol : (i) Nitrating mixture (ii) Zinc dust What is the action of phosphorous pentachloride on ethyl methyl ether?

Hint:

The reaction of ethers with PCl\(_5\) is a useful method for preparing alkyl halides. The C-O bonds on both sides of the ether oxygen are cleaved. Remember that phenol's reaction with zinc dust is a classic reduction that converts it back to its parent arene.

Answer 1

Reactions on Phenol

[(i)] Nitrating mixture (conc. HNO\(_3\) + conc. H\(_2\)SO\(_4\)): The -OH group of phenol is highly activating. Reacting phenol with a nitrating mixture results in the substitution of nitro groups at the ortho and para positions, forming 2,4,6-trinitrophenol (Picric acid). \[ \text{C}_6\text{H}_5\text{OH} + 3\text{HNO}_3 \xrightarrow{\text{conc. H}_2\text{SO}_4} \text{C}_6\text{H}_2(\text{NO}_2)_3\text{OH} + 3\text{H}_2\text{O} \]
[(ii)] Zinc dust: When phenol is heated with zinc dust, it undergoes dehydroxylation (removal of the -OH group) to form benzene. \[ \text{C}_6\text{H}_5\text{OH} + \text{Zn} \xrightarrow{\Delta} \text{C}_6\text{H}_6 + \text{ZnO} \]
Action of PCl\(_5\) on Ethyl Methyl Ether When ethyl methyl ether (CH\(_3\)OC\(_2\)H\(_5\)) is heated with phosphorus pentachloride (PCl\(_5\)), the ether linkage breaks, and both alkyl groups are converted into their corresponding alkyl chlorides. \[ \text{CH}_3\text{OC}_2\text{H}_5 + \text{PCl}_5 \xrightarrow{\Delta} \text{CH}_3\text{Cl} + \text{C}_2\text{H}_5\text{Cl} + \text{POCl}_3 \]