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Question #45071
The Question
Consider the following two-step reaction sequence involving 4-hydroxy-3-methoxybenzaldehyde (Vanillin):
Step 1: The substrate is treated with exactly one equivalent of methylmagnesium bromide () in dry THF at 273 K, producing an intermediate complex and evolving a gas. Step 2: The resulting mixture is then treated with one equivalent of methyl iodide () in DMF and gently warmed, yielding the major organic product .
Identify the major product .
Options
- A.
4-(1-hydroxyethyl)-2-methoxyphenol
- B.
3,4-dimethoxybenzaldehyde
- C.
1-(3,4-dimethoxyphenyl)ethan-1-ol
- D.
4-hydroxy-3-methoxy-2-methylbenzaldehyde
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
Electrophile vs Nucleophile|Grignard Reagent Sensitivity|Aldehydes, Ketones, and Carboxylic Acids
Why This Question Is Tricky
Common Mistakes
The trap exploits the 'Nucleophile vs.
Base' dichotomy of Grignard reagents.
Students typically view Grignard reagents purely as nucleophiles and immediately predict an attack on the electrophilic aldehyde to form a secondary alcohol.
The hidden variable is the presence of the acidic phenolic proton.
Because acid-base reactions are kinetically and thermodynamically favored over nucleophilic addition, the Grignard reagent is entirely quenched by the proton, forming a phenoxide.
Failing to account for this 'lethal collision' leads to the incorrect textbook addition product.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Organic Chemistry – Some Basic Principles and Techniques - Class 11 Part 2 |
| Concept | Electrophile vs Nucleophile |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |