Check sibling questions

Account for the following: 

(A) Aniline cannot be prepared by the ammonolysis of chlorobenzene under normal conditions. 

(B) N-ethylethanamine boils at 329.3K and butanamine boils at 350.8K, although both are isomeric in nature. 

(C) Acylation of aniline is carried out in the presence of pyridine.

Answer

(A)

  • In case of chlorobenzene, the C—Cl bond acquires a partial double bond character due to conjugation. 
  • This lends it stability and makes it quite difficult to break .

PARTIAL DOUBLE BOND CHARACTER IN CHLOROBENZENE - Teachoo.jpg

  • So under the normal conditions , ammonolysis of chlorobenzene does not yield aniline
  • Therefore, we use indirect ways to obtain aniline through chlorobenzene.

CONVERSION OF CHLOROBENZENE TO ANILINE - Teachoo-Question 4(i).jpg

(B)

  • Primary and secondary amines are engaged in intermolecular association due to hydrogen bonding between nitrogen of one and hydrogen of another molecule. 
  • The intermolecular association is more in 1-1 primary amines due to the presence of three hydrogen atoms . Butanamine is a primary amine.
  • In secondary amines there are two hydrogen atoms available for hydrogen bonding . So, the intermolecular association is less than that in primary amines .
  • N-ethylethanamine is a secondary amine.

STRUCTURE OF N-ETHYLETHANAMINE  - Teachoo.jpg

STRUCTURE OF BUTANAMINE  - Teachoo.jpg

  (C)

  • Catalysts are added to reactions to speed up the process by making the reaction more likely to happen , that is, increasing its spontaneity .
  • During the acylation HCl is formed during the reaction.
  • A strong base, pyridine , is added in order to remove the Hydrogen from Aniline and form HCl

This shifts the equilibrium to the right hand side, making the reaction more spontaneous.

ACYLATION OF ANILINE  - Teachoo.jpg

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Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 12 years. He provides courses for Maths and Science at Teachoo.