Question

The decreasing order of basic character of the three amines and ammonia is :
A. $NH_3>CH_3NH_2>C_2H_5NH_2>C_6H_5NH_2$
B. $C_2H_5NH_2>CH_3NH_2>NH_3>C_6H_5NH_2$
C. $C_6H_5NH_2>C_2H_5NH_2>CH_3NH_2>NH_3$.
D. $CH_3NH_2>C_2H_5NH_2> C_6H_5NH_2>NH_3$.

Answer 1

Hint: Basicity of species defines the basic character of the species. As the electron donating power of a species increases its basic character also increases. It depends on several factors like- the groups attached, the resonance effect etc.

Complete step-by-step answer:Stability factor of base:
-An electron donating group attached to a species its basicity increases because the electron donating group increases electron density on the base atom and hydrogen ion accepting tendency of the species increases.
-But an electron withdrawing group decreases the basicity of a species.

Stability comparison:
-Ethylamine or $C_2H_5NH_2$ has an electron donating alkly group attached with an amine group which increases its electron donating power and basic character increases.

-Methyl amine or $CH_3NH_2$ has an electron donating alkly group attached with an amine group which increases its electron donating power and basic character increases.

The electron donating power of methyl group is less than ethyl group.

-Phenyl amine or $C_6H_5NH_2$ has an electron withdrawing aryl group attached with an amine group which decreases its electron donating power and basic character decreases.

-Ammonia or $NH_3$ is moderately basic.

Thus the order of basic character is as follows-
$C_2H_5NH_2>CH_3NH_2>NH_3>C_6H_5NH_2$.

Option ‘B’ is correct

Note: Basic character or basicity of a species defines the electron donating power. The acidic character or acidity of a species defines electron accepting power. Basicity increases with increase in ease of pair of electrons donation. Base produce from weak acid is a strong conjugate base.