Question

Arrange the following compounds in the order of their acidic strengths:
$\underset{I}{C{H}_3-\underset{\underset{O}{||}}{C}-C{H}_3}\underset{II}{C{H}_3-\underset{\underset{O}{||}}{C}-\underset{\underset{O}{||}}{C}-C{H}_3}\underset{III}{C{H}_3-\underset{\underset{O}{||}}{C}-C{H}_2-\underset{\underset{O}{||}}{C}-C{H}_3}$

• A. I > II > III
• B. III > II > I
• C. I > III > II
• D. III > I > II

Answer 1

The correct option is B III > II > I

Acidic strength $\propto$ stability of its conjugate base or anion stability
Electron withdrawing group stablises anion.
stability of conjugate base (carbanion) is in the order:
$C{H}_3-\underset{\underset{\underset{\text{-M effect}}{O}}{||}}{C}-\stackrel{\ominus }{CH}-\underset{\underset{\underset{\text{-M effect}}{O}}{||}}{C}-C{H}_3>C{H}_3-\underset{\underset{\underset{\text{-I effect}}{O}}{||}}{C}-\underset{\underset{\underset{\text{-M effect}}{O}}{||}}{C}-\stackrel{\ominus }{C{H}_2}>C{H}_3-\underset{\underset{\underset{\text{-M effect}}{O}}{||}}{C}-\stackrel{\ominus }{C{H}_2}$
Hence acidity order is III > II > I