Arrange primary, secondary and tertiary amines in decreasing order of basicity in water and explain — JEE Chemistry
Arrange primary, secondary and tertiary amines in decreasing order of basicity in water and explain.
1 Answer
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· 2mo ago
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In water: $(CH_3)_2NH > CH_3NH_2 > (CH_3)_3N > NH_3$
Explanation:
- Inductive effect: more alkyl groups → more electron donation → increases basicity. Predicts 3° > 2° > 1°.
- Solvation (hydration): $NH_4^+$ conjugate acid must be stabilised by H-bonding. 3° ammonium ion cannot H-bond well → destabilised.
- Balance of these effects gives 2° as most basic in aqueous solution.
$$(CH_3)_2NH > CH_3NH_2 > (CH_3)_3N > NH_3 (in water)$$
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Discussion (4)
O
Pro tip: memorise the standard result, it reappears in many problems.
N
How do we know the approximation is valid here?
T
Thanks a ton, I was stuck on this exact problem for an hour.
D
Pro tip: memorise the standard result, it reappears in many problems.