Question

Explain the basic nature of amines with a suitable example.

Answer 1

The basic nature of amines is due to the presence of a lone pair of electrons on the nitrogen atom.

1. Lewis theory: In terms of Lewis theory, amines are bases because they can share a lone pair of electrons on ‘N’ atom with an electron-deficient species. For example, trimethylamine shares its lone pair of electrons with the electron-deficient boron trifluoride.
   \[\ce{Me3N{:} + BF3 -> Me3\overset{⊕}{N} - \overset{Θ}{B}F3}\]
2. Lowry-Bronsted theory: The basic nature of amines is explained by writing the following equilibrium. In this equilibrium amine accepts H⁺, hence an amine is a LowryBronsted base. For a stronger base, this equilibrium shifts towards the right, thereby, for stronger bases, the K_b value is larger or the pK_b value is smaller.