Question 1

Why does aniline direct electrophilic substitution mainly to ortho and para positions?

Accepted Answer

The nitrogen atom of the amino group has a lone pair that can delocalise into the benzene pi system by resonance. This increases electron density especially at the two ortho carbons and the para carbon, making those positions more attractive to electrophiles.

Question 2

What happens when aniline reacts with bromine water?

Accepted Answer

Aniline undergoes rapid electrophilic bromination at the 2, 4 and 6 positions. The ring hydrogens at those positions are replaced by bromine atoms, producing 2,4,6-tribromoaniline, which appears as a white precipitate.

Question 3

Why does strong acid change the directing behaviour of aniline?

Accepted Answer

In strongly acidic medium, the amino group can accept a proton to form the anilinium ion, C6H5NH3+. The positively charged nitrogen has no lone pair available for resonance donation, so the ring becomes deactivated. Direct mixed-acid nitration still gives chiefly ortho- and para-products, while protonation explains the possibility of minor meta substitution.

Question 4

Why is acetanilide prepared before nitrating aniline?

Accepted Answer

Acetylation converts aniline into acetanilide, C6H5NHCOCH3. The acetyl group reduces excessive activation while retaining ortho/para direction, allowing smoother nitration that gives p-nitroacetanilide as the main product.

Question 5

What is obtained after hydrolysis of p-nitroacetanilide?

Accepted Answer

Hydrolysis removes the acetyl protecting group and gives p-nitroaniline. The para nitro group remains on the benzene ring, so the product is not regenerated aniline.

Aniline's Ring: Activated but Tricky

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