JEE Main · 2023 · 25 Jan 2023 · Shift 1 · Compounds Containing Nitrogen

The correct order in aqueous medium of basic strength in case of methyl substituted amines is :

(A) $Me_{2} NH > MeNH_{2} > Me_{3} N > NH_{3}$ ✓ Correct
(B) $Me_{2} NH > Me_{3} N > MeNH_{2} > NH_{3}$
(C) $NH_{3} > Me_{3} N > MeNH_{2} > Me_{2} NH$
(D) $Me_{3} N > Me_{2} NH > MeNH_{2} > NH_{3}$

Answer: (A)

Solution

In water the basic strength of the methylamines is governed jointly by the electron density the methyl groups push onto nitrogen and by how well the resulting cation is stabilised through hydrogen bonding to water. Each added methyl group raises the electron density but also removes an N-H available for solvation and adds steric bulk. Dimethylamine strikes the best balance and is the strongest base, followed by methylamine, then trimethylamine whose poor solvation drops it below methylamine, with ammonia weakest. The decreasing order of basic strength is dimethylamine, methylamine, trimethylamine, ammonia.

JEE Main · 2023 · 25 Jan 2023 · Shift 1 · Single correct option

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JEE Main · 2023 · 25 Jan 2023 · Shift 1 · Compounds Containing Nitrogen

Solution

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