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Question #44339
The Question
Consider the tautomerization of the nucleobase Uracil (pyrimidine-2,4(1H,3H)-dione) from its dominant physiological diketo form to its mutagenic C4-monoenol form at . Determine the values of the following structural parameters:
Total number of hybridized atoms in the diketo tautomer. Formal charge of N3 in the specific zwitterionic resonance contributor of the diketo form where a -bond exists between N3 and C4. Number of nitrogen atoms possessing a localized lone pair in an orbital in the C4-monoenol tautomer. Formal charge of N3 in the C4-monoenol tautomer.
Calculate the sum:
Options
- A.
8
- B.
9
- C.
10
- D.
11
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
Formal Charge Calculation|Nitrogenous Base Keto-Enol Tautomerism|Peptide Bond Planarity
Why This Question Is Tricky
Common Mistakes
This question tests the 'Hidden Variable' of orbital rehybridization and formal charge redistribution during keto-enol tautomerism in nitrogenous bases.
Students often incorrectly assign sp3 hybridization to amide/imide nitrogens by merely counting VSEPR domains, ignoring resonance (V1 trap).
Furthermore, they frequently fail to recognize that in the enol (lactim) form, the nitrogen becomes an imine where the lone pair is orthogonal to the pi-system in an sp2 orbital, not a p-orbital (V3 trap).
Finally, calculating the formal charge on the zwitterionic vs. neutral enol forms forces students to connect valence bond theory with the biological consequence of altered H-bonding potential.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Chemical Bonding and Molecular Structure - Class 11 Part 1 |
| Concept | Formal Charge Calculation |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |