Question:
The correct increasing order of basic strength of the following amines/compounds is:
(I) \(C_6H_5NH_2\) (Aniline)
(II) \(NH_3\) (Ammonia)
(III) \(C_6H_5CH_2NH_2\) (Benzylamine)
(IV) \(C_2H_5NH_2\) (Ethylamine)
(V) \((C_2H_5)_2NH\) (Diethylamine)
The correct increasing order of basic strength of the following amines/compounds is:
(I) \(C_6H_5NH_2\) (Aniline)
(II) \(NH_3\) (Ammonia)
(III) \(C_6H_5CH_2NH_2\) (Benzylamine)
(IV) \(C_2H_5NH_2\) (Ethylamine)
(V) \((C_2H_5)_2NH\) (Diethylamine)
(I) \(C_6H_5NH_2\) (Aniline)
(II) \(NH_3\) (Ammonia)
(III) \(C_6H_5CH_2NH_2\) (Benzylamine)
(IV) \(C_2H_5NH_2\) (Ethylamine)
(V) \((C_2H_5)_2NH\) (Diethylamine)
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Aromatic amines are weaker bases because resonance delocalizes the lone pair on nitrogen. Aliphatic amines are stronger due to the \(+I\) effect of alkyl groups.
Updated On: Jun 3, 2026
- \(C_6H_5NH_2 < NH_3 < C_6H_5CH_2NH_2 < C_2H_5NH_2 < (C_2H_5)_2NH\)
- \(NH_3 < C_6H_5NH_2 < C_6H_5CH_2NH_2 < C_2H_5NH_2 < (C_2H_5)_2NH\)
- \(C_6H_5CH_2NH_2 < C_6H_5NH_2 < NH_3 < C_2H_5NH_2 < (C_2H_5)_2NH\)
- \(C_2H_5NH_2 < (C_2H_5)_2NH < C_6H_5NH_2 < NH_3\)
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Verified By Collegedunia
The Correct Option is A
Solution and Explanation
Concept:
The basic strength of amines depends upon the availability of the lone pair of electrons on the nitrogen atom for donation to a proton (\(H^+\)). Greater the availability of the lone pair, greater will be the basic strength.
The important factors affecting basicity are:
• Inductive Effect (\(+I\) effect): Alkyl groups donate electron density toward nitrogen, increasing basicity.
• Resonance Effect: Delocalization of lone pair decreases its availability and decreases basicity.
• Solvation Effect: Stabilization of protonated species in aqueous medium affects basicity.
• Steric Hindrance: Bulky groups can reduce protonation efficiency.
Step 1: Analyzing Aniline \((C_6H_5NH_2)\).
In aniline, the lone pair on nitrogen is directly involved in resonance with the benzene ring. \[ C_6H_5NH_2 \longleftrightarrow \text{Resonance structures} \] Due to resonance:
• Lone pair becomes delocalized.
• Electron density on nitrogen decreases.
• Availability of lone pair for protonation decreases. Hence, Aniline is the weakest base among all the given compounds. \[ C_6H_5NH_2 < NH_3 \]
Step 2: Analyzing Ammonia \((NH_3)\).
Ammonia contains a localized lone pair on nitrogen. There is:
• No resonance effect.
• No electron donating alkyl group. Thus, Ammonia is more basic than Aniline but weaker than aliphatic amines.
Step 3: Analyzing Benzylamine \((C_6H_5CH_2NH_2)\).
In Benzylamine:
• The \(-NH_2\) group is attached to \(sp^3\) hybridized carbon.
• Lone pair cannot participate in resonance with benzene ring. Therefore:
• Lone pair remains available.
• Basicity increases compared to ammonia. Thus: \[ NH_3 < C_6H_5CH_2NH_2 \]
Step 4: Analyzing Ethylamine and Diethylamine.
Ethyl groups show strong \(+I\) effect.
• Ethylamine has one ethyl group.
• Diethylamine has two ethyl groups. More alkyl groups increase electron density on nitrogen. Thus: \[ C_2H_5NH_2 < (C_2H_5)_2NH \] Also both are stronger bases than ammonia and benzylamine.
Step 5: Combining all observations.
Final increasing order of basic strength becomes: \[ C_6H_5NH_2 < NH_3 < C_6H_5CH_2NH_2 < C_2H_5NH_2 < (C_2H_5)_2NH \] Hence, the correct option is: \[ \boxed{(A)} \]
• Inductive Effect (\(+I\) effect): Alkyl groups donate electron density toward nitrogen, increasing basicity.
• Resonance Effect: Delocalization of lone pair decreases its availability and decreases basicity.
• Solvation Effect: Stabilization of protonated species in aqueous medium affects basicity.
• Steric Hindrance: Bulky groups can reduce protonation efficiency.
Step 1: Analyzing Aniline \((C_6H_5NH_2)\).
In aniline, the lone pair on nitrogen is directly involved in resonance with the benzene ring. \[ C_6H_5NH_2 \longleftrightarrow \text{Resonance structures} \] Due to resonance:
• Lone pair becomes delocalized.
• Electron density on nitrogen decreases.
• Availability of lone pair for protonation decreases. Hence, Aniline is the weakest base among all the given compounds. \[ C_6H_5NH_2 < NH_3 \]
Step 2: Analyzing Ammonia \((NH_3)\).
Ammonia contains a localized lone pair on nitrogen. There is:
• No resonance effect.
• No electron donating alkyl group. Thus, Ammonia is more basic than Aniline but weaker than aliphatic amines.
Step 3: Analyzing Benzylamine \((C_6H_5CH_2NH_2)\).
In Benzylamine:
• The \(-NH_2\) group is attached to \(sp^3\) hybridized carbon.
• Lone pair cannot participate in resonance with benzene ring. Therefore:
• Lone pair remains available.
• Basicity increases compared to ammonia. Thus: \[ NH_3 < C_6H_5CH_2NH_2 \]
Step 4: Analyzing Ethylamine and Diethylamine.
Ethyl groups show strong \(+I\) effect.
• Ethylamine has one ethyl group.
• Diethylamine has two ethyl groups. More alkyl groups increase electron density on nitrogen. Thus: \[ C_2H_5NH_2 < (C_2H_5)_2NH \] Also both are stronger bases than ammonia and benzylamine.
Step 5: Combining all observations.
Final increasing order of basic strength becomes: \[ C_6H_5NH_2 < NH_3 < C_6H_5CH_2NH_2 < C_2H_5NH_2 < (C_2H_5)_2NH \] Hence, the correct option is: \[ \boxed{(A)} \]
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