Consider the following statements about the electrophilic substitution reactions of anisole.
(A) Anisole undergoes bromination with bromine in ethanoic acid even in the absence of iron(III) bromide catalyst.
(B) In the bromination of anisole with bromine in ethanoic acid, the ortho isomer is obtained as the major product.
(C) Anisole reacts with ethanoyl chloride in the presence of anhydrous aluminium chloride to give 2-methoxyacetophenone and 4-methoxyacetophenone.
(D) The alkoxy group (–OR) of an alkyl aryl ether deactivates the aromatic ring towards electrophilic substitution.
Which of the statements given above are incorrect? 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 anisole the methoxy group pushes electron density into the benzene ring by resonance, in the same way as the –OH group of phenol. The ring becomes more reactive, and the ortho and para positions become electron rich.
(A) Anisole undergoes bromination with bromine in ethanoic acid even in the absence of iron(III) bromide catalyst. — Correct statement. The ring is activated by the methoxy group, so no Lewis acid is needed.
(B) In the bromination of anisole with bromine in ethanoic acid, the ortho isomer is obtained as the major product. — Incorrect statement. The para isomer is the major product (90% yield); o-bromoanisole is the minor product.
\( \displaystyle \ce{C6H5OCH3 + Br2} \xrightarrow{\text{ethanoic acid}} p\text{-}\ce{BrC6H4OCH3}\ (\text{major}) + \ce{HBr} \)
(C) Anisole reacts with ethanoyl chloride in the presence of anhydrous aluminium chloride to give 2-methoxyacetophenone and 4-methoxyacetophenone. — Correct statement. In this Friedel-Crafts acylation the acetyl group enters the ortho and para positions of the activated ring.
(D) The alkoxy group (–OR) of an alkyl aryl ether deactivates the aromatic ring towards electrophilic substitution. — Incorrect statement. The alkoxy group activates the ring and is ortho, para directing.
NCERT (2026-27 edition):
7.6.3 Chemical Reactions – “2. Electrophilic substitution
The alkoxy group (-OR) is ortho, para directing and activates the aromatic ring towards electrophilic substitution in the same way as in phenol.”
“(i) Halogenation: Phenylalkyl ethers undergo usual halogenation in the benzene ring, e.g., anisole undergoes bromination with bromine in ethanoic acid even in the absence of iron (III) bromide catalyst. It is due to the activation of benzene ring by the methoxy group. Para isomer is obtained in 90% yield.”
“(ii) Friedel-Crafts reaction: Anisole undergoes Friedel-Crafts reaction, i.e., the alkyl and acyl groups are introduced at ortho and para positions by reaction with alkyl halide and acyl halide in the presence of anhydrous aluminium chloride (a Lewis acid) as catalyst.”
\( \displaystyle \ce{C6H5OCH3 + CH3COCl} \xrightarrow{\text{Anhyd. } \ce{AlCl3}} \underset{\text{(minor)}}{\text{2-Methoxyacetophenone}} + \underset{\text{(major)}}{\text{4-Methoxyacetophenone}} \)