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Question #44433

Difficulty: 8/10 | 🟢 Free

The Question

An optically active compound X\textbf{X} (\ceC16H14O4\ce{C16H14O4}) is treated with exactly one equivalent of periodic acid (\ceHIO4\ce{HIO4}) at 298 K to yield two moles of a single compound Y\textbf{Y}. Compound Y\textbf{Y} gives a positive Tollens' test (silver mirror) but fails to produce a red precipitate when heated with Fehling's solution. Instead, the strongly basic conditions of Fehling's solution cause Y\textbf{Y} to undergo a rapid rearrangement to an intermediate that, upon careful acidification, yields compound Z\textbf{Z}. Let Csp2C_{sp^2} be the number of sp2sp^2 hybridized carbon atoms and Csp3C_{sp^3} be the number of sp3sp^3 hybridized carbon atoms in a single molecule of Z\textbf{Z}. What is the value of (Csp2−Csp3)(C_{sp^2} - C_{sp^3})?

Options

  • A.

    5

  • B.

    6

  • C.

    7

  • D.

    8

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|Tollens vs. Fehling Specificity

Why This Question Is Tricky

Common Mistakes

Tests the chemoselectivity of HIO4 cleavage (vicinal diol vs alpha-hydroxy ketone) and the specific reactivity of alpha-keto aldehydes.

Students often falsely assume all aldehydes reduce Fehling's solution or that failure is solely due to aromaticity.

The hidden variable is the strong base in Fehling's solution, which triggers a rapid internal Cannizzaro rearrangement of phenylglyoxal into mandelic acid, outcompeting the oxidation process.

Quick Facts About This Question

Question Information

SubjectChemistry
ChapterAlcohols, Phenols, and Ethers - Class 12
ConceptGlycol Periodic Acid Cleavage
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree