Question

The end product in the reaction sequence would be:
Ethylamine $ \xrightarrow{{HN{O_{21}}}}A\xrightarrow{{PC{L_5}}}B\xrightarrow{{N{H_3}}}C $
(A) Ethyl cyanide
(B) Ethylamine
(C) Methylamine
(D) Acetamide

Answer 1

Hint: The reaction sequence is the propagation of the reaction or the linked reaction in which the product of the first reaction acts as a reactant for the second reaction. Here ethylamine $ C{H_3}C{H_2}N{H_2} $ is the root of the reaction. So, we will follow the sequence of the reaction to predict the end product of the reaction sequence.

Complete step by step answer:
We will start with the root of the reaction sequence which is given to us as ethylamine. Now in the first part of the reaction ethylamine is reacted with nitrous acid which forms the product $ A $ . Then $ A $ is reacted with phosphorus pentachloride which gives us a hint about the product $ A $ that it may be alcohol according to the reactions of phosphorus pentachloride. So, now we have got the idea about the sequence of the reaction. So, now we will write the expected products of the reaction sequence, so, the reaction sequence is as follows.
 $ {C_2}{H_5}N{H_2}\xrightarrow{{HN{O_2}}}{C_2}{H_5}OH\xrightarrow{{PC{l_5}}}{C_2}{H_5}Cl\xrightarrow{{N{H_3}}}{C_2}{H_5}N{H_2} $
From the above reaction sequence, we can observe that when ethylamine is reacted with nitrous acid it gives ethyl alcohol which is the product $ A \to {C_2}{H_5}OH $ . Now when ethyl alcohol reacts with phosphorus pentachloride it gives ethyl chloride which is the product $ B \to {C_2}{H_5}Cl $ . Now when ethyl chloride reacts with ammonia it will give ethylamine which is formed as the compound $ C \to {C_2}{H_5}N{H_2} $ . The compound $ C \to {C_2}{H_5}N{H_2} $ ethylamine is formed as the end-product of the reaction sequence.
Therefore, the correct option is (B).

Note:
The end-product formed in the reaction sequence ethylamine $ C \to {C_2}{H_5}N{H_2} $ is a colorless liquid or gas. Ethylamine is the primary aliphatic amine which has a hydrogen bond which is responsible for their solubility in water. Ethylamine is a conjugate base of ethylammonium.