Before You Begin
Question #44939
The Question
Consider the basicity of the following aromatic amines in an aqueous medium at : (I) \ce{C6H5NH2} (II) \ce{2-CH3-C6H4NH2} (III) \ce{2-C(CH3)3-C6H4NH2} (IV) \ce{4-CH3-C6H4NH2}
Which of the following represents the correct decreasing order of their basic strength ()?
Options
- A.
IV > I > II > III
- B.
III > II > IV > I
- C.
IV > II > III > I
- D.
III > IV > II > I
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
Ortho-Effect in Anilines|Basicity-Solvation Competition|Inductive Effect Trends
Why This Question Is Tricky
Common Mistakes
This question tests the 'Ortho-Effect' in anilines and the competition between electronic effects and solvation energy.
Students often fall into the trap of assuming that the massive +I effect and Steric Inhibition of Resonance (SIR) caused by the tert-butyl group in compound (III) will make the lone pair highly localized and thus highly basic.
However, they overlook the 'Hidden Variable': basicity in aqueous media is heavily dictated by the thermodynamic stability of the conjugate acid.
The extreme steric bulk of the tert-butyl group prevents water molecules from solvating the anilinium ion, making compound (III) exceptionally weak as a base despite its electron-donating substituent.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Amines - Class 12 |
| Concept | Ortho-Effect in Anilines |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |