See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Tautomerism Analysis **Tautomerism** is the dynamic equilibrium between constitutional isomers that differ in the position of a hydrogen atom and a double bond, typically involving keto-enol interconversion. ## Option-by-Option Evaluation: **(A) 2,2-dimethylpropanal** $(CH_3)_3C-CHO$ - Aldehyde with no α-hydrogen atoms (the carbon bearing H is quaternary) - Cannot undergo keto-enol tautomerism - ✗ No tautomerism **(B) 2,2-dimethyl-1-nitropropane** $(CH_3)_3C-CH_2-NO_2$ - Has α-hydrogens adjacent to the electron-withdrawing $-NO_2$ group - Can exist as: keto form $(CH_3)_3C-CH_2-NO_2$ ⇌ enol form $(CH_3)_3C-CH=N(OH)O$ - The nitro group stabilizes the conjugate base, enabling tautomerism - ✓ **Shows tautomerism** **(C) 2,4-pentanedione** $CH_3-CO-CH_2-CO-CH_3$ - β-diketone with α-hydrogens between two carbonyl groups - Keto form ⇌ enol form: hydrogen shifts between equivalent positions - Highly stable enol form due to conjugation and hydrogen bonding - ✓ **Shows prominent tautomerism** **(D) Benzophenone** $(C_6H_5)_2C=O$ - Aromatic ketone with no α-hydrogens (sp² carbons only) - Cannot form tautomeric forms - ✗ No tautomerism **Answer: B and C** exhibit tautomerism due to the presence of α-hydrogens adjacent to electron-withdrawing groups that can undergo keto-enol interconversion.