Question

Amongst the following the strongest base in aqueous medium is:

• A. ${\left({\mathrm{CH}}_3\right)}_2\mathrm{NH}$
• B. ${\mathrm{CH}}_3{\mathrm{NH}}_2$
• C. ${\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{NHCH}}_3$
• D. ${\mathrm{NCCH}}_2{\mathrm{NH}}_2$

Answer 1

The correct option is A

${\left({\mathrm{CH}}_3\right)}_2\mathrm{NH}$

Explanation for correct option:

A. ${\left({\mathrm{CH}}_3\right)}_2\mathrm{NH}$

Amines:

• Amines are Nitrogen-containing compounds.
• They are both aliphatic as well as aromatic in nature.
• Amines have nitrogen as a central metal atom which has a lone pair of electrons over it. Due to this lone pair of electron amines are basic in nature.
• The strength of basicity of amines depends upon the availability of lone pair electrons and resonance.
• The order of basicity for general amines is $3^{\circ }>2^{\circ }>1{}^{\circ }$, Due to $\left(+\mathrm{I}\right)$, electron density on nitrogen atoms increases and thereby strength of basicity also increases
• The aromatic amines are less basic than aliphatic amines as the alkyl group in aliphatic amines shows $\left(+\mathrm{I}\right)$ effect to increase the electron density. However, in the case of aromatic amine, lone pairs of electrons participate in resonance.

Therefore, the secondary amine i.e. ${\left({\mathrm{CH}}_3\right)}_2\mathrm{NH}$ is the most basic in nature.

Explanation for incorrect options:

B. ${\mathrm{CH}}_3{\mathrm{NH}}_2$

• It is a primary amine that is less basic than the secondary amine.

C. ${\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{NHCH}}_3$

• Aromatic amine is less basic than aliphatic amine.

D. ${\mathrm{NCCH}}_2{\mathrm{NH}}_2$

• It is a primary aliphatic amine.

Hence, the correct option is A i.e. ${\left({\mathrm{CH}}_3\right)}_2\mathrm{NH}$ is the strongest base in an aqueous solution.