See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Tautomerism in $(CH_3)_2NH$ **Understanding Tautomerism:** Tautomerism requires structural isomers that interconvert via migration of a hydrogen atom (usually) between two atoms, typically involving shift of a double bond. **Analysis of Option (A): $(CH_3)_2NH$** $(CH_3)_2NH$ can exhibit **imino-enamine tautomerism**: $$\text{Imino form: } (CH_3)_2N=CH_2 \rightleftharpoons \text{Enamine form: } CH_2=C(NH_2)(CH_3)$$ or alternatively: $$CH_3-CH=N(CH_3) \rightleftharpoons CH_2=C(NH)(CH_3)$$ The nitrogen lone pair can participate in tautomeric shifts through hydrogen migration, creating constitutional isomers. **Why others don't work:** - **(B) $(CH_3)_3CNO_2$**: Stable nitro compound; no mobile hydrogen for tautomerization - **(C) $R_3CNO_2$**: Quaternary carbon structure prevents H-migration - **(D) $RCH_2NO_2$**: While it has an α-hydrogen, nitro compounds don't readily undergo typical tautomerism due to strong $N=O$ bond stability **Answer: (A)** exhibits tautomerism because the secondary amine allows proton migration between nitrogen and adjacent carbons, generating different structural isomers in equilibrium.