chapter 13 Amines Class 12 Chemistry Textbook Solution

3. Answer the following

ii. Explain the basic nature of amines with suitable example.


i. Lewis Theory:

  • According to Lewis theory, amines are considered bases because they have the ability to share a lone pair of electrons located on the nitrogen (N) atom with an electron-deficient species.
  • For instance, trimethylamine (Me3N) can share its lone pair of electrons with the electron-deficient boron trifluoride (BF3).
  • The reaction can be represented as follows: Me3N + BF3 → Me3N⁺ B⁻ F3

ii. Lowry-Bronsted Theory:

  • The basic nature of amines can also be explained using the Lowry-Bronsted theory.
  • In this theory, a base is defined as a substance capable of accepting a proton (H⁺).
  • Amines, being proton acceptors, are considered Lowry-Bronsted bases.
  • In equilibrium, an amine accepts H⁺, demonstrating its basic nature.

iii. Strength of Amines as Bases:

  • The strength of amines as bases can be assessed by examining the equilibrium of their proton acceptance reactions.
  • A stronger base will shift the equilibrium toward the right, indicating a higher tendency to accept protons.
  • Consequently, stronger bases have larger Kₙ (equilibrium constant for the base dissociation) values or smaller pKₙ (negative logarithm of Kₙ) values.

This way, amines exhibit their basic nature according to both Lewis and Lowry-Bronsted theories, with their strength as bases determined by the equilibrium constants or pKₙ values

13 Amines Class 12 Chemistry Textbook Solution page 297