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Question #44012
The Question
Compound \ce{X} (5,5-dimethoxy--dimethyl-7-oxooctanamide) is treated with an excess of 2,4-dinitrophenylhydrazine in an aqueous acidic medium (pH 3.0) at 298 K. The reaction mixture is subjected to mild heating to yield a thermodynamically stable major organic product \ce{Y}.
Determine the Degree of Unsaturation (Double Bond Equivalent) of the major product \ce{Y}.
Options
- A.
10
- B.
15
- C.
8
- D.
9
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|Nucleophilic Acyl Substitution
Why This Question Is Tricky
Common Mistakes
The question tests three critical exceptions and mechanistic traps in carbonyl chemistry: (1) Chemoselectivity and Resonance: Students must recognize that amides do not undergo nucleophilic acyl substitution with 2,4-DNP.
The nitrogen lone pair delocalizes into the carbonyl, rendering it insufficiently electrophilic. (2) Hidden Functional Groups: The ketal must be identified and hydrolyzed under the acidic conditions of Brady's reagent to reveal the hidden ketone, forming a 1,3-diketone. (3) Thermodynamic Sink (The Primary Trap): The most lethal trap is the reaction of the 1,3-diketone with 2,4-DNP.
A reflexive application of 'ketone + DNP -> hydrazone' leads to the erroneous bis-hydrazone product (DU = 15).
Advanced students will recognize that 1,3-diketones react with hydrazines to form thermodynamically stable, aromatic pyrazole derivatives, consuming only one equivalent of the reagent.
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 |