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Question #44015
The Question
An organic compound \textbf{A} (4-oxopentanal) is treated with 1.0 equivalent of 2,4-dinitrophenylhydrazine in a mildly acidic medium (pH 3.5) to yield the major product \textbf{B}. Compound \textbf{B} is then dissolved in dry ether at 273 K and treated with exactly 2.0 equivalents of methylmagnesium bromide (), followed by careful quenching with aqueous to yield compound \textbf{C} as the major organic product. Identify the IUPAC name of \textbf{C}.
Options
- A.
4-hydroxy-4-methylpentanal 2,4-dinitrophenylhydrazone
- B.
5-(2,4-dinitrophenylhydrazono)hexan-2-ol
- C.
4-oxopentanal N-methyl-N-(2,4-dinitrophenyl)hydrazone
- D.
5-(2-(2,4-dinitrophenyl)hydrazinyl)-2-methylhexan-2-ol
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
Reaction with DNP|Grignard Reaction Pathways|Enolate Regioselectivity
Why This Question Is Tricky
Common Mistakes
The question tests the student's ability to navigate a multi-step synthesis involving chemoselectivity and a critical 'Hidden Variable'.
Students must first recognize that DNP selectively protects the aldehyde due to lower steric hindrance and higher electrophilicity.
The major trap lies in the subsequent Grignard addition: students often forget that the N-H proton of a 2,4-DNP hydrazone is highly acidic due to the two nitro groups.
They might erroneously assume that 2.0 equivalents of Grignard will result in double nucleophilic addition (attacking both the ketone and the C=N bond) or act as an alkylating agent.
Recognizing that the first equivalent is consumed in an acid-base reaction is the key to predicting the correct regioselectivity and final product.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Aldehydes, Ketones, and Carboxylic Acids - Class 12 |
| Concept | Reaction with DNP |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |