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Question #44005
The Question
Ethyl benzoate is treated with excess \ce{CH3MgBr} in dry ether at , followed by acidic workup to yield the major organic product Q. Q is then subjected to reductive amination conditions (\ce{CH3NH2}, \ce{NaBH3CN}, , ) to yield R. Finally, R is treated with Hinsberg reagent (\ce{PhSO2Cl}) in excess aqueous \ce{NaOH}, and the resulting mixture is extracted with dichloromethane. What is the molar mass of the major organic compound isolated from the dichloromethane layer?
Options
- A.
136 g/mol
- B.
275 g/mol
- C.
150 g/mol
- D.
135 g/mol
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
Grignard Reaction Pathways|Esterification Reversibility|Hinsberg Reagent Selectivity
Why This Question Is Tricky
Common Mistakes
This problem tests the 'over-addition' mechanism of Grignard reagents to esters.
A common trap is assuming the reaction stops at the ketone (acetophenone).
If a student falls for this, they will predict a successful reductive amination to form a secondary amine (N-methyl-1-phenylethanamine), which then reacts with Hinsberg reagent to form an insoluble sulfonamide (Molar mass = ) that extracts into the organic layer.
Recognizing that the initial ester is completely consumed to form an unreactive tertiary alcohol is the key to identifying the correct final product.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Aldehydes, Ketones, and Carboxylic Acids - Class 12 |
| Concept | Grignard Reaction Pathways |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |