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NEET 2019 · ChemistryPrevious Year Question

The correct order of the basic strength of methyl-substituted amines in aqueous solution is:

Answer: (A) . \textbf{Answer:} (a) \textbf{Solution:} In aqueous solution the basicity of amines is governed by three competing factors: the effect (methyl groups donate electron density to N), steric hindrance (bulky groups hinder protonation), and solvation/H-bonding stabilisation of the conjugate cation (more N-H bonds give more H-bonding stabilisation).

  1. A.✓
  2. B.
  3. C.
  4. D.

Correct Answer

(A)

Solution & Explanation

\textbf{Answer:} (a) \textbf{Solution:} In aqueous solution the basicity of amines is governed by three competing factors: the effect (methyl groups donate electron density to N), steric hindrance (bulky groups hinder protonation), and solvation/H-bonding stabilisation of the conjugate cation (more N-H bonds give more H-bonding stabilisation). The net result for methylamines in water is . Trimethylamine is least basic because steric crowding and poor solvation outweigh the inductive effect.

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