How basic is each amine?
"How basic is each amine?" is a free, interactive Class 12 Chemistry simulation for NEET and JEE, built on the lesson "Basic character of amines" in Amines. The pKb values are the ones NCERT gives for water. The picture shows the groups on nitrogen and how many N–H hydrogens the protonated cation keeps for hydrogen bonding with water; the bars compare the whole series. Smaller pKb, stronger base. Alkyl amines beat ammonia; in water 2° is strongest and the 3° place depends on the group size. Arylamines are far weaker because the lone pair is delocalised. JEE Main asked 57 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
From the lesson Basic character of amines in Amines. Change the values and watch what happens.
In JEE Main
42 shifts analysed
57 questions from Amines across the 42 JEE Main shifts Lumi has analysed (2017–2026).
The idea behind it
NCERT §9.6
- The lone pair on nitrogen makes amines Lewis bases. They form salts with acids, and NaOH gives the amine back. Amine salts dissolve in water but not in ether, which lets amines be separated from non-basic organic compounds.
- Base strength is measured by Kb, or pKb = −log Kb; the larger Kb (smaller pKb), the stronger the base. Ammonia has pKb 4.75.
- pKb in water. Methyl series: 1° methanamine 3.38, 2° N-methylmethanamine 3.27, 3° N,N-dimethylmethanamine 4.22. Ethyl series: 1° ethanamine 3.29, 2° N-ethylethanamine 3.00, 3° N,N-diethylethanamine 3.25. Aromatic: benzenamine (aniline) 9.38, N-methylaniline 9.30, N,N-dimethylaniline 8.92; phenylmethanamine (benzylamine) 4.70.
- Alkyl groups push electrons (+I) onto nitrogen, making the lone pair more available, and spread the positive charge of the ammonium ion. So aliphatic amines are stronger bases than ammonia; their pKb values run from 3 to 4.22.
- In the gas phase basicity follows the +I effect: tertiary > secondary > primary > NH₃.
- In water, the ammonium ions are also stabilised by hydrogen bonding to water (solvation). Smaller ions with more N–H hydrogens are solvated best, favouring primary > secondary > tertiary, the reverse of the inductive order. Groups bigger than –CH₃ also hinder that hydrogen bonding sterically.
- The balance of inductive effect, solvation and steric hindrance gives the aqueous orders (C₂H₅)₂NH > (C₂H₅)₃N > C₂H₅NH₂ > NH₃ and (CH₃)₂NH > CH₃NH₂ > (CH₃)₃N > NH₃.
- Aniline is a much weaker base than ammonia: its lone pair is conjugated with the ring. Aniline has five resonance structures, the anilinium ion only two (Kekulé), so protonation costs aniline stability.
- On substituted anilines, electron-releasing groups (–OCH₃, –CH₃) raise basic strength; electron-withdrawing groups (–NO₂, –SO₃H, –COOH, –X) lower it.
- Worked order, strongest first: (C₂H₅)₂NH > C₂H₅NH₂ > NH₃ > C₆H₅NH₂.
Questions
3 answers
- What does the "How basic is each amine?" simulation show?
- The pKb values are the ones NCERT gives for water. The picture shows the groups on nitrogen and how many N–H hydrogens the protonated cation keeps for hydrogen bonding with water; the bars compare the whole series.
- Does JEE Main ask questions from Amines?
- Yes. JEE Main asked 57 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
- Is this simulation free?
- Yes. It is free and runs in the browser on a phone or a laptop. It belongs to the lesson "Basic character of amines" in Amines (Class 12 Chemistry).
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