MHT CET202520 Apr 2025Evening ShiftChemistryAminesActual
Which from following is the most stable species?
Options
- ANH ₄⁺
- BR - + N H ₃
- CR ₂ + N H ₂
- DR ₃ + N H
Correct answer
D. R ₃ + N H
Step-by-step solution
Ammonium ion stability depends on three competing factors: the inductive effect of alkyl groups, solvation through hydrogen bonding, and steric hindrance to solvation. Alkyl groups donate electron density inductively, stabilizing positive charge. Solvation in aqueous environments favors ions with more hydrogens for hydrogen bonding. Steric hindrance from bulky groups reduces solvation effectiveness. Experimental pKa values for methyl-substituted ammonium ions reveal the stability order: pKa [( CH ₃)₂ + N H ₂] (10.7