Question 7 of 39intermediate🔍 AnalyzeShort Answer2 marks

Which of the following is an appropriate set of reactants for the preparation of 1-methoxy-4-nitrobenzene and why? (i) Br + CH₃ONa (ii) ONa + CH₃Br

Correct Answer

(ii) ONa + CH₃Br is the appropriate set of reactants for the preparation of 1-methoxy-4-nitrobenzene.

Exercise: Intext Questions | Q: 7.11 | (Page Page 28)
For More Understanding

Explanation

According to the textbook context, Williamson synthesis involves the reaction of an alkoxide ion with an alkyl halide. The context clearly states that 'Better results are obtained if the alkyl halide is primary. In case of secondary and tertiary alkyl halides, elimination competes over substitution.' In option (ii), CH₃Br is a primary alkyl halide, which will undergo substitution reaction with sodium 4-nitrophenoxide to give the desired ether. In option (i), the aryl halide (bromonitrobenzene) would not be suitable as aryl halides do not undergo nucleophilic substitution easily.

Solution Steps

  1. Step 1: Identify that Williamson synthesis requires an alkoxide ion and an alkyl halide.

  2. Step 2: Note from context that primary alkyl halides give better results as elimination competes with substitution in secondary and tertiary alkyl halides.

  3. Step 3: In option (ii), CH₃Br is a primary alkyl halide, making it suitable for substitution reaction with sodium 4-nitrophenoxide.

  4. Step 4: Conclude that option (ii) is the appropriate set of reactants.

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