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Question #44027

Difficulty: 8/10 | 🟢 Free

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 (1∘1^\circ), secondary (2∘2^\circ), and tertiary (3∘3^\circ) amines.

Let AmaxA_{max} and AminA_{min} be the most basic and least basic amines (among the 1∘,2∘1^\circ, 2^\circ, and 3∘3^\circ amines) derived from \ce{CH3I} in aqueous solution at 298 K. Let BmaxB_{max} and BminB_{min} be the most basic and least basic amines (among the 1∘,2∘1^\circ, 2^\circ, and 3∘3^\circ amines) derived from \ce{C2H5I} in aqueous solution at 298 K.

Calculate the value of (x+y)(x + y), where xx is the total number of α\alpha-hydrogens in AmaxA_{max} and AminA_{min}, and yy is the total number of α\alpha-hydrogens in BmaxB_{max} and BminB_{min}.

(Note: α\alpha-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: 3∘>2∘>1∘3^\circ > 2^\circ > 1^\circ).

In water, the stability of the conjugate acid via hydrogen bonding (solvation energy) competes with the inductive effect.

For methylamines, solvation dominates, making 3∘3^\circ the least basic (2∘>1∘>3∘2^\circ > 1^\circ > 3^\circ).

For ethylamines, steric crowding reduces solvation, making 1∘1^\circ the least basic (2∘>3∘>1∘2^\circ > 3^\circ > 1^\circ).

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 3∘3^\circ to 1∘1^\circ.

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

SubjectChemistry
ChapterAmines - Class 12
ConceptBasicity-Solvation Competition
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree