Question

The correct order of decreasing basic strength in aqueous solution of the following is :

• A. (C₂H₅)₃N > C₂H₅NH₂ > (C₂H₅)₂NH
• B. (C₂H₅)₂NH > C₂H₅NH₂ > (C₂H₅)₃N
• C. C₂H₅NH₂ > (C₂H₅)₂NH > (C₂H₅)₃N
• D. (C₂H₅)₂NH > (C₂H₅)₃N > C₂H₅NH₂

Hint:

Ethyl amines in water: 2-amine > 3-amine > 1-amine (solvation + steric + inductive balance).

Answer 1

The Correct Option is D

Recall the NCERT result for ethyl-substituted amines in aqueous medium. Although in the gas phase basicity rises 1° < 2° < 3° (pure inductive effect), in $water$ the solvation of the ammonium ion and steric factors rearrange the order. For the ethyl series the measured order is diethylamine > triethylamine > ethylamine.
Matching this to the options, only (D) reads (C₂H₅)₂NH > (C₂H₅)₃N > C₂H₅NH₂. Correct option: (D).