Williamson synthesis is an important method for the preparation of ethers.
Consider the following statements and identify the correct statements
(A) This method is not applicable for preparation of symmetrical ethers.
(B) This method is used for the preparation of both symmetrical and unsymmetrical ethers .
(C) This involves SN1 attack of an alkoxide on primary alkyl halide.
(D) Ethers containing substituted alkyl groups (secondary or tertiary ) can also be prepared by this method.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (B) and (D) only
In Williamson synthesis, an alkyl halide reacts with a sodium alkoxide. The alkoxide ion is a strong nucleophile and attacks the alkyl halide in a single step, so the reaction is SN2.
The alkoxide ion is also a strong base. With a primary alkyl halide, substitution takes place and an ether is formed. With a secondary or tertiary alkyl halide, elimination competes and an alkene is the main product. So, to make an ether with a bulky group, the bulky group is put in the alkoxide and the halide is kept primary:
\( \displaystyle \ce{(CH3)3C-ONa + CH3-Br -> (CH3)3C-O-CH3 + NaBr} \)
\( \displaystyle \ce{(CH3)3C-Br + CH3ONa -> (CH3)2C=CH2 + CH3OH + NaBr}\quad(\text{elimination}) \)
(A) This method is not applicable for preparation of symmetrical ethers. — Incorrect. If R and R′ are the same group, a symmetrical ether is formed, so the method does work for them.
(B) This method is used for the preparation of both symmetrical and unsymmetrical ethers. — Correct. R and R′ may be the same or different.
(C) This involves SN1 attack of an alkoxide on primary alkyl halide. — Incorrect. The reaction happens in one step with no carbocation, so it is SN2, not SN1.
(D) Ethers containing substituted alkyl groups (secondary or tertiary) can also be prepared by this method. — Correct. This works when the secondary or tertiary group is taken as the alkoxide, as shown in the first equation above.
NCERT (2026-27 edition):
Williamson Synthesis
