The Question is from neet-chemistry alcohols-phenols-ethers , and it was created by the author Mr. S M HUSSAIN

Question

Which of the following reactions is NOT a suitable method for the preparation of anisole (methoxybenzene)?

Mr. S M HUSSAIN · Accepted Answer

## CORE INFORMATION
✓ **Answer**: C
## CONCEPT FRAMEWORK
 **Primary Concept**: Williamson ether synthesis and other methods of ether preparation
 **Related Topics**: Electrophilic aromatic substitution, nucleophilic aromatic substitution
 **Prerequisites**: Understanding of reaction mechanisms, reactivity of phenols and aryl halides.
## SOLUTION PATHWAY
**Given Information**:
  The target molecule is anisole ($C_6H_5OCH_3$). Four different methods for its preparation are given.
  [Important conditions]: We need to identify the reaction that does not produce anisole.
**Method & Steps**:
 1. Analyze each reaction mechanism.
  Reasoning: Williamson ether synthesis is a common method for preparing ethers.  Diazomethane is a powerful methylating agent.  Direct alkylation of phenols can be problematic due to competing reactions.  The reaction of aryl halides with alkoxides requires a catalyst like copper(I) iodide (CuI).
  Formula/Rule: Williamson ether synthesis: $R-O^- + R'-X ightarrow R-O-R' + X^-$
 2. Evaluate the suitability of each option for producing anisole.
  Working: 
        A. Williamson synthesis using sodium phenoxide ($C_6H_5O^-$) and methyl iodide ($CH_3I$) is a valid method: $C_6H_5O^- + CH_3I ightarrow C_6H_5OCH_3 + I^-$
        B. Reaction of phenol ($C_6H_5OH$) with diazomethane ($CH_2N_2$) is also a suitable method for methylation of the phenolic hydroxyl group: $C_6H_5OH + CH_2N_2 ightarrow C_6H_5OCH_3 + N_2$
        C. Reaction of phenol with methyl iodide is unlikely to produce anisole in good yield.  Phenol is acidic and will likely deprotonate before methylation occurs.  A strong base is required to form the phenoxide ion, which is a better nucleophile.
        D. Reaction of bromobenzene ($C_6H_5Br$) with sodium methoxide ($CH_3O^-$) in the presence of CuI is an example of Ullmann ether synthesis, a variation of nucleophilic aromatic substitution. This method is suitable for preparing aryl ethers.
 3. Identify the unsuitable reaction.
  Result: Option C, the direct reaction of phenol with methyl iodide, is not a suitable method for preparing anisole in good yield due to the low nucleophilicity of the phenoxide ion and competing acid-base reactions.
  Verification: The other three options are known and established methods for anisole synthesis.
 ## OPTION ANALYSIS
A ✓: Williamson ether synthesis is a standard method for ether preparation.  Sodium phenoxide is a good nucleophile.
B :x: Reaction of phenol with diazomethane is a valid method for methylation.
C :x:  Direct reaction of phenol with methyl iodide is inefficient due to the need for a strong base to deprotonate the phenol to form the phenoxide ion, which is a much better nucleophile.
D :x: Ullmann ether synthesis is a viable method for making aryl ethers using aryl halides.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Assuming that all alkyl halides will react directly with phenols to form ethers:  Phenols require activation (deprotonation) to become better nucleophiles.
  2.Overlooking the need for a catalyst in certain aryl ether syntheses (like Ullmann conditions):  CuI is crucial for Ullmann ether synthesis.
 **Quick Tips**:
  1.Remember that the phenoxide ion is a much better nucleophile than phenol itself.
  2.Understand the different reaction mechanisms and their respective limitations.

Mr. S M HUSSAIN · Answer

Williamson ether synthesis using sodium phenoxide and methyl iodide

Mr. S M HUSSAIN · Answer

Reaction of phenol with diazomethane

Mr. S M HUSSAIN · Answer

The correct Option is "Reaction of phenol with methyl iodide"

Mr. S M HUSSAIN · Answer

Reaction of bromobenzene with sodium methoxide in the presence of CuI

NEET Chemistry Alcohols, Phenols And Ethers MCQs

Select Topic

Question Tags

NEET Subjects

Our Bots

Company