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Question #44427
The Question
Compound \textbf{P} (butan-2-one) is subjected to the following reaction sequence:
- \ce{LDA} (1.05 eq), \ce{THF},
- \ce{PhCH2Br} (1.0 eq)
The major organic product \textbf{Q} is isolated and subsequently treated with excess \ce{I2} in aqueous \ce{NaOH} at . Which of the following statements correctly identifies \textbf{Q} and the observation from the final step?
Options
- A.
\textbf{Q} is 1-phenylpentan-3-one; no yellow precipitate is formed.
- B.
\textbf{Q} is 3-methyl-4-phenylbutan-2-one; a yellow precipitate of \ce{CHI3} is formed.
- C.
\textbf{Q} is 1-phenylpentan-3-one; a yellow precipitate of \ce{CHI3} is formed.
- D.
\textbf{Q} is 3-methyl-4-phenylbutan-2-one; no yellow precipitate is formed.
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
Iodoform Reaction Requirements|Enolate Regioselectivity
Why This Question Is Tricky
Common Mistakes
This problem tests the intersection of Enolate Regioselectivity (Kinetic vs.
Thermodynamic control) and the structural prerequisites of the Haloform Reaction.
The primary trap exploits the student's initial recognition of butan-2-one as a methyl ketone.
If a student incorrectly predicts thermodynamic enolate formation (at the \ce{-CH2-} group), the resulting product (3-methyl-4-phenylbutan-2-one) retains the methyl ketone moiety and would falsely yield a positive Iodoform test.
The 'Hidden Variable' is the irreversible destruction of the methyl ketone functional group under kinetic alkylation conditions, rendering the final diagnostic test negative.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Alcohols, Phenols, and Ethers - Class 12 |
| Concept | Iodoform Reaction Requirements |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |