Assertion & Reason Test: Amines - NEET MCQ

Aromatic primary amines cannot be prepared by Gabriel phthalimide synthesis as it  is used for the preparation of aliphatic primary amines and not aromatic primary amines.

When phthalimide is treated with aqueous or ethanolic potassium hydroxide, it forms its potassium salt. This salt, when heated with an alkyl halide and then subjected to alkaline hydrolysis, yields the corresponding primary amine.

Aromatic primary amines cannot be prepared by this method because aryl halides do not undergo nucleophilic substitution with the anion formed by phthalimide.


So, the assertion is wrong.
Reason: 
Aryl halides do not undergo nucleophilic substitution with anion formed by phthalimide.

So, the reason is wrong.

Hence, both assertion and reason are wrong.

Assertion (A) states that N,N-diethylbenzene sulphonamide is insoluble in alkali.

N,N-diethylbenzene sulphonamide has a benzene ring attached to a sulphonamide (SO₂NH) with two ethyl groups on nitrogen. Solubility in alkali typically requires acidic hydrogens to react with OH⁻ ions. However, N,N-diethylbenzene sulphonamide lacks these acidic hydrogens, making it insoluble in alkali.

Hence, Assertion is correct.
Reason (R) states that the sulphonyl group is a strong electron-withdrawing group.

The SO₂ group does withdraw electrons, reducing electron density on nitrogen. However, this electron withdrawal doesn’t directly cause the insolubility; the lack of acidic hydrogen is the main reason.

Hence, Reason is correct but does not explain the assertion.

The correct option is A If both assertion and reason are true and the reason is the correct explanation of the assertion.
HNO₃+2H₂SO₄⇋ 2HSO₄⁻+ NO₂⁺+ H₃O⁺

Only a small amount of HCl is needed to reduce nitro compounds to amines using iron scrap and HCl with steam. This is because FeCl₂, formed during the reaction, undergoes hydrolysis, releasing hydrochloric acid that can then sustain the reaction.

Fe + 2HCl → FeCl₂ + H₂

With Steam

FeCl₂ + H₂O(g) → Fe(OH)₂ + 2HCl

Reason:

FeCl₂ formed gets hydrolyzed and releases HCl during the reaction.
So, it can be used further in the reaction. So, the Reason is a correct statement and it explains the assertion.

Hence,  Both assertion and reason are correct statements and reason is the correct explanation of assertion.

The Hoffmann bromamide degradation reaction prepares primary amines by treating an amide with bromine in an aqueous or ethanolic sodium hydroxide solution. The resulting amine has one carbon atom less than the original amide.

Therefore, the assertion is incorrect because Hoffmann’s bromamide reaction involves amides rather than primary amines, even though the product is a primary amine.

Reason:
Primary amines are less basic than secondary amines because secondary amines have more electron-donating alkyl groups, which enhance their basicity. Thus, the reason statement is also incorrect.

Consequently, both the assertion and reason are wrong.

-NH₂  is o- and p- directing in electrophilic substitution reactions due to excess of electron or negative charge over o- and p- positions because of its various resonating Structures. 

Aniline cannot undergo a Friedel-Crafts reaction because its amino group (-NH₂) donates electrons to the benzene ring, making it highly reactive. However, this same amino group also reacts with the Lewis acid catalyst (like AlCl₃), inhibiting the reaction. Thus, while Friedel-Crafts is indeed an electrophilic substitution reaction, this alone doesn’t explain aniline's lack of reactivity.

Both the assertion and reason are correct, but the reason does not explain the assertion.

In the reaction, the NH₂ group is protected by an acetyl group because it is highly reactive due to the lone pair on the nitrogen in aniline. The incoming NO₂ group tends to accept this lone pair effectively. Therefore, acetylation of the NH₂ group is performed to reduce its reactivity towards the incoming NO₂ group.