Question

Identify X and Y in the following sequence

A.\[{\rm{X = KCN,Y = LiAl}}{{\rm{H}}_{\rm{4}}}\]
​B. \[{\rm{X = KCN,Y = }}{{\rm{H}}_{\rm{3}}}{{\rm{O}}^{\rm{ + }}}\]
C. \[{\rm{X = C}}{{\rm{H}}_{\rm{3}}}{\rm{Cl,Y = AlC}}{{\rm{l}}_{\rm{3}}}{\rm{/HCl}}\]
D. \[{\rm{X = C}}{{\rm{H}}_{\rm{3}}}{\rm{N}}{{\rm{H}}_{\rm{2}}}{\rm{,Y = HN}}{{\rm{O}}_{\rm{2}}}\]

Answer 1

Hint: Alkyl halides on reaction with alcoholic potassium cyanide or sodium cyanide form alkyl cyanide. Alkyl cyanide on reduction with lithium aluminium hydride forms primary amines.

Complete Step by Step Solution:
Amines are formed by the replacement of one, two or all three hydrogen atoms of ammonia by alkyl or aryl groups.

A. Bromoethane in reaction with alcoholic potassium cyanide forms propionitrile.
Propionitrile then on reaction lithium aluminium hydride undergoes reduction.
It forms the primary amine having one carbon atom more than the parent ethyl bromide.
Thus, it forms propan-1-amine as the product.
In the given reaction, the last product formed is also propan-1-amine.

Image: Reaction of bromoethane with KCN.

So, option A is correct.

B. Bromoethane on reaction with KCN will form propionitrile.
Propionitrile in presence of hydronium ion will undergo acid hydrolysis to form propionic acid.

Image: Reaction of propionitrile with hydronium ion.

So, it will not form propan-1-amine.
Thus, option B is incorrect.

C. Bromoethane and chloromethane will not react with each other. So, this reaction will not happen.
So, option C is incorrect.

D. Bromoethane on reaction with ethanenitrile will form N-Methylethanamine and hydrogen bromide.

Image: Reaction of bromoethane with ethanenitrile.

N-Methylethanamine will not react with nitrous acid. It is because nitrous acid reacts with\[{\rm{R - N}}{{\rm{H}}_{\rm{2}}}{\rm{orAr - N}}{{\rm{H}}_{\rm{2}}}\]to form alkyl diazonium chloride or aryl diazonium chloride i.e., \[{\rm{R - N}}_2^ + {\rm{ClorAr - N}}_2^ + {\rm{C}}{{\rm{l}}^{\rm{ - }}}\].

But in N-Methylethanamine, there are only two hydrogen atoms attached to Nitrogen atoms.
So, option D is incorrect.

So, option A is correct.

Note: Bromoethane reacts with KCN to form propionitrile. Propionitrile on reaction with lithium aluminium hydride undergoes reduction to form propan-1-amine. Propan-1-amine has one carbon more than bromoethane. While attending to the question, one must choose the option in which the end product is propan-1-amine.