Question:
Choose the correct order of basicity of the following.
\[
(a)\ (C_2H_5)_2NH
\qquad
(b)\ C_2H_5NH_2
\qquad
(c)\ NH_3
\qquad
(d)\ C_6H_5NH_2
\]
Choose the correct order of basicity of the following.
\[
(a)\ (C_2H_5)_2NH
\qquad
(b)\ C_2H_5NH_2
\qquad
(c)\ NH_3
\qquad
(d)\ C_6H_5NH_2
\]
Show Hint
Alkyl groups increase basicity through the \(+I\) effect, whereas resonance decreases basicity.
\[
\text{Secondary amine}
\gt
\text{Primary amine}
\gt
NH_3
\gt
\text{Aniline}
\]
because the lone pair of aniline is delocalized into the benzene ring.
Updated On: Jul 18, 2026
- \(a\gt c\gt d\gt b\)
- \(a\gt b\gt c\gt d\)
- \(d\gt a\gt c\gt b\)
- \(d\gt c\gt b\gt a\)
Show Solution
Verified By Collegedunia
The Correct Option is B
Solution and Explanation
Step 1: Identify the given compounds.
\[ (a)=(C_2H_5)_2NH \] Diethylamine (secondary amine)
\[ (b)=C_2H_5NH_2 \] Ethylamine (primary amine)
\[ (c)=NH_3 \] Ammonia
\[ (d)=C_6H_5NH_2 \] Aniline
Step 2: Recall the factors affecting basicity.
Basicity depends on the availability of the lone pair of electrons on nitrogen for donation. Alkyl groups show a \(+I\) (electron-releasing) effect, which increases electron density on nitrogen and increases basicity.
Therefore, \[ \text{Secondary amine}\gt \text{Primary amine}\gt \text{Ammonia} \]
Step 3: Compare diethylamine, ethylamine and ammonia.
Diethylamine contains two ethyl groups that donate electron density to nitrogen through the \(+I\) effect. Hence, its lone pair is most available. \[ (C_2H_5)_2NH \gt C_2H_5NH_2 \gt NH_3 \]
Step 4: Compare aniline with ammonia.
In aniline, the lone pair on nitrogen is involved in resonance with the benzene ring. \[ \text{Lone pair} \longrightarrow \text{delocalized into the aromatic ring} \] As a result, the lone pair becomes less available for protonation. Therefore, aniline is less basic than ammonia. \[ NH_3 \gt C_6H_5NH_2 \]
Step 5: Write the overall order.
Combining all comparisons: \[ (C_2H_5)_2NH \gt C_2H_5NH_2 \gt NH_3 \gt C_6H_5NH_2 \] That is, \[ a\gt b\gt c\gt d \]
Step 6: Final conclusion.
Hence, the correct order of basicity is \[ \boxed{a\gt b\gt c\gt d} \] Therefore, option (2) is correct.
\[ (a)=(C_2H_5)_2NH \] Diethylamine (secondary amine)
\[ (b)=C_2H_5NH_2 \] Ethylamine (primary amine)
\[ (c)=NH_3 \] Ammonia
\[ (d)=C_6H_5NH_2 \] Aniline
Step 2: Recall the factors affecting basicity.
Basicity depends on the availability of the lone pair of electrons on nitrogen for donation. Alkyl groups show a \(+I\) (electron-releasing) effect, which increases electron density on nitrogen and increases basicity.
Therefore, \[ \text{Secondary amine}\gt \text{Primary amine}\gt \text{Ammonia} \]
Step 3: Compare diethylamine, ethylamine and ammonia.
Diethylamine contains two ethyl groups that donate electron density to nitrogen through the \(+I\) effect. Hence, its lone pair is most available. \[ (C_2H_5)_2NH \gt C_2H_5NH_2 \gt NH_3 \]
Step 4: Compare aniline with ammonia.
In aniline, the lone pair on nitrogen is involved in resonance with the benzene ring. \[ \text{Lone pair} \longrightarrow \text{delocalized into the aromatic ring} \] As a result, the lone pair becomes less available for protonation. Therefore, aniline is less basic than ammonia. \[ NH_3 \gt C_6H_5NH_2 \]
Step 5: Write the overall order.
Combining all comparisons: \[ (C_2H_5)_2NH \gt C_2H_5NH_2 \gt NH_3 \gt C_6H_5NH_2 \] That is, \[ a\gt b\gt c\gt d \]
Step 6: Final conclusion.
Hence, the correct order of basicity is \[ \boxed{a\gt b\gt c\gt d} \] Therefore, option (2) is correct.
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