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 has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 12 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.