The increasing order of the acidity of the α-hydrogen of the following compounds is :

Solution

Chemistry ma’am · 3 steps

Ask how well the C=O can hold the negative charge: two carbonyls win, a donating N or O next door loses.

1. What decides acidity. Removing an α-hydrogen leaves a carbanion that the carbonyl stabilises by resonance, moving the charge onto oxygen as an enolate. The more the carbonyl can take that charge, the more acidic the α-hydrogen.
2. Competing donors. In an ester or amide, the lone pair on O or N already pushes into the C=O, so the carbonyl has less pull left for the carbanion. N donates more strongly than O, so the amide carbonyl is the weakest acceptor.

   Compound	Next to the C=O	Enolate stabilisation	Approx. pKₐ
   (D) CH₃CON(CH₃)₂	N(CH₃)₂, strong lone-pair donor	weakest	about 30
   (C) CH₃COOCH₃	OCH₃, weaker donor	weak	about 25
   (A) CH₃COCH₃	CH₃, no lone-pair competition	good, one carbonyl	about 20
   (B) PhCOCH₂COPh	a second C=O on the other side	best: charge spread over two O atoms and the rings	about 9

3. So. The increasing order of acidity is (D) < (C) < (A) < (B), which is option (d).

The idea to keep. For α-H acidity, look at what sits next to the carbonyl. A lone-pair donor (N more than O) weakens it; a second carbonyl on the other side makes the CH₂ strongly acidic.

Answer from the NTA final answer key. Solution by PrepWiser.