Question 30 of 39intermediate🔧 ApplyShort Answer4 marks

Write the names of reagents and equations for the preparation of the following ethers by Williamson's synthesis: (i) 1-Propoxypropane (ii) Ethoxybenzene (iii) 2-Methoxy-2-methylpropane (iv) 1-Methoxyethane

(i)
Answer

1-Propoxypropane Reagents: Sodium propoxide and Propyl bromide Equation: CH₃CH₂CH₂ONa + CH₃CH₂CH₂Br → CH₃CH₂CH₂-O-CH₂CH₂CH₃ + NaBr

(ii)
Answer

Ethoxybenzene Reagents: Sodium phenoxide and Ethyl bromide Equation: C₆H₅ONa + C₂H₅Br → C₆H₅-O-C₂H₅ + NaBr

(iii)
Answer

2-Methoxy-2-methylpropane Reagents: Sodium 2-methylpropan-2-olate (Sodium tert-butoxide) and Methyl bromide Equation: (CH₃)₃CONa + CH₃Br → (CH₃)₃C-O-CH₃ + NaBr

(iv)
Answer

1-Methoxyethane Reagents: Sodium methoxide and Ethyl bromide Equation: CH₃ONa + C₂H₅Br → CH₃-O-C₂H₅ + NaBr

Explanation

Williamson's synthesis involves the reaction of a sodium alkoxide with an alkyl halide. For symmetrical ethers like 1-propoxypropane, either combination works. For unsymmetrical ethers, the alkyl halide should preferably be primary or methyl to avoid elimination reactions. For aromatic ethers like ethoxybenzene, sodium phenoxide is reacted with alkyl halide. For 2-methoxy-2-methylpropane, sodium tert-butoxide must be used with methyl halide (not the reverse) to prevent elimination from the tertiary halide.

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