Question

Given below are two statements:
Statement I: Aniline reacts with con. \( H_2SO_4 \) followed by heating at 453–473 K gives p-aminobenzene sulphonic acid, which gives blood red colour in the 'Lassaigne's test'.
Statement II: In Friedel-Craft's alkylation and acylation reactions, aniline forms salt with the \( AlCl_3 \) catalyst. Due to this, nitrogen of aniline acquires a positive charge and acts as a deactivating group.
In the light of the above statements, choose the correct answer from the options given below:

• A. Statement I is false but Statement II is true
• B. Both Statement I and Statement II are false
• C. Statement I is true but Statement II is false
• D. Both Statement I and Statement II are true

Answer 1

The Correct Option is D

To solve this problem, let's analyze each statement individually and provide the correct reasoning behind why both statements are true.

• Statement I: Aniline reacts with concentrated \(H_2SO_4\) followed by heating at 453–473 K to form p-aminobenzene sulphonic acid, which gives a blood red color in the 'Lassaigne's test'.

Explanation:

• In concentrated \(H_2SO_4\), aniline undergoes sulfonation to form p-aminobenzene sulphonic acid (also known as sulphanilic acid) when heated in the range of 453–473 K.
• This compound, upon Lassaigne's test for sulphur, forms sodium thiocyanate, which reacts with ferric chloride to give a blood-red color.

This establishes that Statement I is true.

• Statement II: In Friedel-Craft's alkylation and acylation reactions, aniline forms a salt with the \(AlCl_3\) catalyst. Due to this, the nitrogen of aniline acquires a positive charge and acts as a deactivating group.

Explanation:

• Aniline is a base and reacts with Lewis acids such as \(AlCl_3\) to form a salt. The nitrogen atom of aniline gets protonated, acquiring a positive charge.
• This positively charged nitrogen significantly reduces the electron density of the aromatic ring, making it less reactive in the Friedel-Craft's reactions, hence acting as a deactivating group.

This confirms that Statement II is also true.

Since both statements are true, the correct option is: Both Statement I and Statement II are true.

Answer 2

Statement I is correct because aniline does react with concentrated sulfuric acid and, upon heating, forms p-aminobenzene sulfonic acid, which gives a blood red color in Tassaigne’s test.

Statement II is also correct as in Friedel-Crafts alkylation and acylation reactions, aniline forms a salt with the \(\text{AlCl}_3\) catalyst. This interaction results in a positive charge on nitrogen, causing it to act as a deactivating group, making further substitution reactions difficult on the benzene ring.

Thus, both statements are true.