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Question #44027
The Question
Consider the exhaustive ammonolysis of methyl iodide (\ce{CH3I}) and ethyl iodide (\ce{C2H5I}) in separate reaction vessels, followed by the isolation of the respective primary (), secondary (), and tertiary () amines.
Let and be the most basic and least basic amines (among the , and amines) derived from \ce{CH3I} in aqueous solution at 298 K. Let and be the most basic and least basic amines (among the , and amines) derived from \ce{C2H5I} in aqueous solution at 298 K.
Calculate the value of , where is the total number of -hydrogens in and , and is the total number of -hydrogens in and .
(Note: -hydrogens are the hydrogen atoms attached to the carbon atoms directly bonded to the nitrogen atom).
Options
- A.
21
- B.
20
- C.
25
- D.
15
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
Basicity-Solvation Competition|Ammonolysis Complexity|Inductive Effect Trends
Why This Question Is Tricky
Common Mistakes
The question tests the 'Chemical Exception' of amine basicity in aqueous media.
Students often assume a linear relationship based on the +I effect (gas phase: ).
In water, the stability of the conjugate acid via hydrogen bonding (solvation energy) competes with the inductive effect.
For methylamines, solvation dominates, making the least basic ().
For ethylamines, steric crowding reduces solvation, making the least basic ().
The trap is failing to differentiate the steric impact of methyl vs. ethyl groups on the hydration sphere, which flips the least basic amine from to .
Distractors represent students applying the gas-phase logic (Option B), applying methyl logic to ethyl (Option C), or applying ethyl logic to methyl (Option D).
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Amines - Class 12 |
| Concept | Basicity-Solvation Competition |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |