See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Analyzing Base Strength in Water **Step 1: Identify the structures** - (A) Pyrrole (5-membered aromatic ring with N) - (B) Pyrroline (5-membered partially unsaturated ring with N) - (C) Pyridine (6-membered aromatic ring with N) - (D) Piperidine (6-membered saturated ring with N) **Step 2: Consider electron availability on nitrogen** For basicity, the lone pair on nitrogen must be available to accept a proton ($H^+$). - **(A) & (C)**: Aromatic rings require the lone pair to participate in aromaticity. The N lone pair is delocalized into the π-system, making it unavailable for protonation. - **(B)**: The lone pair is partially involved in maintaining partial aromaticity; weaker base than saturated analogs. - **(D)**: Piperidine is fully saturated. The lone pair on N is localized and **not involved in any π-system**. **Step 3: Compare basicity** The localized lone pair in piperidine is most electron-rich and most available for protonation: $$\text{Piperidine} + H^+ \rightarrow \text{Piperidinium}^+ \quad (\text{most favorable})$$ **Answer: (D) Piperidine** — The saturated, non-aromatic structure allows the nitrogen lone pair to remain fully available, making it the strongest base in water.