Question

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R) 
Assertion (A): \(\alpha\)-halocarboxylic acid on reaction with dil \(NH _3\) gives good yield of \(\alpha\)-aminocarboxylic acid whereas the yield of amines is very low when prepared from alkyl halides 
Reason (R): Amino acids exist in zwitter ion form in aqueous medium 
In the light of the above statements, choose the correct answer from the options given below :

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
• B. (A) is not correct but (R) is correct
• C. Both (A) and (R) are correct but (R) is not the correct explanation of (A)
• D. $( A )$ is correct but $( R )$ is not correct

Hint:

Carefully analyze the relationship between the assertion and the reason. Even if both are true independently, the reason might not be the correct explanation for the assertion.

Answer 1

The Correct Option is C

Step 1: Analyze Assertion (A)
α-halocarboxylic acids react with dilute ammonia (NH3) to give a good yield of α-amino carboxylic acids. This is because the carboxyl group (-COOH) increases the reactivity of the α-halo group towards nucleophilic substitution. In contrast, the yield of amines from simple alkyl halides reacting with ammonia is low due to overalkylation, where the initially formed amine can react further with the alkyl halide. Therefore, Assertion (A) is correct.
Step 2: Analyze Reason (R)
Amino acids exist as zwitterions in aqueous solutions and in the solid state. A zwitterion has both positive and negative charges within the same molecule, resulting in a net charge of zero. This is due to the acidic carboxyl group and the basic amino group present in
amino acids. Thus, Reason (R) is correct.
Step 3: Analyze the Relationship between (A) and (R)
While both statements are individually correct, Reason (R) doesn’t explain Assertion
(A). The higher yield of amino acids from α-halocarboxylic acids is due to the enhanced reactivity of the α-halo group, not the zwitterionic nature of amino acids.
The zwitterionic form is a characteristic of the product (amino acid) but doesn’t explain the higher yield compared to the reaction of alkyl halides with ammonia. The correct explanation is the neighboring group participation of the carboxylic group makes the reaction proceed via a two-step process leading to a higher yield.