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Question #44157
The Question
Consider the following substituted anilines at 298 K: (I) Aniline (II) 4-Nitroaniline (III) 2,4,6-Trinitroaniline (IV) 2,6-Di-tert-butyl-4-nitroaniline
Which of the following represents the correct decreasing order of their bond lengths?
Options
- A.
IV > I > II > III
- B.
III > IV > I > II
- C.
IV > III > I > II
- D.
I > II > III > IV
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
Bond Order in Resonance Hybrids|Ortho-Effect in Anilines
Why This Question Is Tricky
Common Mistakes
The question tests the boundary between Steric Inhibition of Resonance (SIR) and conformational locking via Intramolecular Hydrogen Bonding.
Students commonly memorize that 'ortho substituents in aniline cause out-of-plane twisting (SIR), increasing C-N bond length'.
They fall into the trap of applying this to 2,4,6-trinitroaniline (Option B), failing to account for the fact that intramolecular H-bonding overrides steric repulsion, keeping the molecule planar and maximizing resonance.
Conversely, the tert-butyl groups in compound IV cannot H-bond, leading to true SIR and a pure single C-N bond.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Chemical Bonding and Molecular Structure - Class 11 Part 1 |
| Concept | Bond Order in Resonance Hybrids |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |