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Question #44430

Difficulty: 8/10 | 🟢 Free

The Question

Let $\ce{Ar}$ represent the 4-methoxyphenyl group. Compound $\mathbf{X}$ , $\ce{Ar2C(OH)-C(OH)Ph2}$ , is treated with an aqueous solution of $\ce{HIO4}$ containing a catalytic amount of concentrated $\ce{HClO4}$ at 298 K. What is the major organic product formed?

Options

A.
$\ce{Ar2C=O} + \ce{Ph2C=O}$
B.
$\ce{Ar2C(Ph)-C(=O)Ph}$
C.
$\ce{Ph2C(Ar)-C(=O)Ar}$
D.
$\ce{Ar(Ph)C=O} + \ce{Ar(Ph)C=O}$

Check Your Answer

Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Mechanism_Trap

Don't get tricked by the process! Learn the mechanical traps used in competitive exam questions.

Concepts Behind This Question

Glycol Periodic Acid Cleavage|Pinacol-Pinacolone Rearrangement

Why This Question Is Tricky

Common Mistakes

This problem tests the kinetic competition between Periodic Acid cleavage and the Pinacol rearrangement.

Students typically memorize that HIO4 cleaves 1,2-diols (Option A).

The 'Hidden Variable' is the strongly acidic medium combined with a sterically hindered tetraaryl substrate, which suppresses cyclic periodate ester formation.

Furthermore, it features a 'Regioselectivity Trap': students who memorize migratory aptitudes (Ar > Ph) without considering initial carbocation stability will incorrectly choose Option C.

Carbocation stability dictates the leaving group, forcing the Ph group to migrate.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Alcohols, Phenols, and Ethers - Class 12
Concept	Glycol Periodic Acid Cleavage
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free