Question

Recognize the compound C from the following:
 $ {C_2}{H_5}N{H_2}\xrightarrow{{HN{O_2}}}A\xrightarrow{{PC{l_3}}}B\xrightarrow{{N{H_3}}}C $
A) Propane nitrile
B) Methylamine
C) Ethylamine
D) Acetamide

Answer 1

Hint: Amines are the compounds that contain the functional group of $ - N{H_2} $ . Nitrous acid is a weak acid and can be used to convert the amines other than methylamine to alcohols. The alcohols with chlorinating agents like $ PC{l_3} $ form alkyl halides. Action of ammonia on alkyl halides forms amines.

Complete answer:
Chemical compounds are classified based on the functional groups. The chemical compounds that contain the functional group of $ - N{H_2} $ are called amines.
Ethyl amine is an amine with the molecular formula of $ {C_2}{H_5}N{H_2} $ . Nitrous acid is a weak acid with the molecular formula $ HN{O_2} $ . It can convert the ethyl amine to ethyl alcohol.
Ethyl alcohol is an alcohol with the molecular formula of $ {C_2}{H_5}OH $ and contains the functional group of $ - OH $ . Thus, ethyl alcohol is the compound A.
Ethyl alcohol upon treatment with chlorinating agents like phosphorous trichloride, the hydroxyl group can be replaced by chlorine atoms. Thus, ethyl chloride will be formed as the compound B.
The ethyl chloride is an alkyl halide, upon treating the ethyl chloride with ammonia, the chlorine atom can be replaced by an amine group and forms ethylamine. Thus, ethyl amine is compound C.
The chemical reaction will be as follows:
 $ {C_2}{H_5}N{H_2}\xrightarrow{{HN{O_2}}}{C_2}{H_5}OH\xrightarrow{{PC{l_3}}}{C_2}{H_5}Cl\xrightarrow{{N{H_3}}}{C_2}{H_5}N{H_2} $
Option C is the correct one.

Note:
All the amine compounds react with nitrous acid to form alcohols or hydroxyl compounds along with the liberation of nitrogen gas. But methyl amine does not react with nitrous acid and does not liberate nitrogen gas. This reaction is known as Liebermann’s test useful for the identification of amines.