Identify the correct decreasing order of acidic strength for the indicated hydroxyl protons (i), (ii), and (iii) in the following compound:

Step-by-step solution

The acidic strength of a hydroxyl proton depends on the stability of its conjugate base. Deprotonation of the hydroxyl group (ii) yields a conjugate base where the negative charge on the oxygen is in conjugation with the C=C double bond and the C=O group. The resonance allows the negative charge to be delocalized onto the electronegative carbonyl oxygen ( O⁻ - C=C - C=O O=C - C⁻ - C=O O=C - C=C - O⁻ ). This extensive resonance stabilization makes (ii) the most acidic proton. Deprotonation of the hydroxyl group (i)