Question

Arrange the following alcohols in decreasing order of the ease of ionization under acidic conditions.

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

Answer 1

Answer: (C)

I > II > III

Answer 2

The ease of ionization of an alcohol under acidic conditions depends on the stability of the carbocation formed after protonation of the hydroxyl group and loss of water. A more stable carbocation leads to easier ionization.

• Compound (I) (9H-fluoren-9-ol): Forms the fluorenyl carbocation, which is significantly resonance stabilized due to its aromatic nature.
• Compound (II) (9H-xanthen-9-ol): Forms the xanthenyl carbocation, stabilized by resonance into the phenyl rings and donation from the oxygen atom.
• Compound (III) (9H-anthracen-9-ol): Forms the anthracenyl carbocation, stabilized by resonance within the anthracene system.

The relative stability of these carbocations is: Fluorenyl > Xanthenyl > Anthracenyl. Therefore, the decreasing order of ease of ionization is I > II > III.