See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Basicity Order of Nitrogen-Containing Heterocycles ## Key Factors Determining Basicity: **1) Lone Pair Availability:** - Basicity depends on the availability of nitrogen's lone pair for protonation - Lone pairs involved in aromatic delocalization are less available **2) Aromaticity Effect (Most Important):** - **Pyridine** (left, aromatic 6-membered): Lone pair is in sp² orbital, perpendicular to aromatic π-system → **NOT delocalized** → More basic - **Pyrrole** (right, aromatic 5-membered): Lone pair is delocalized into aromatic π-system → Less basic - **Piperidine** (saturated 6-membered): Lone pair in sp³ orbital, non-aromatic → Most basic (but similar to aliphatic amines) ## Basicity Comparison: $$\text{Piperidine} > \text{Pyridine} >> \text{Pyrrole}$$ **Why?** - Piperidine: sp³ lone pair, completely available - Pyridine: sp² lone pair perpendicular to π-system (minimal aromatic contribution from lone pair) - Pyrrole: sp² lone pair delocalized as part of aromatic sextet (least available) ## Option (B) Analysis: $$\text{Piperidine} > \text{Pyridine} > \text{Pyrrole}$$ This correctly reflects: - Highest basicity: saturated aliphatic amine (piperidine) - Intermediate: aromatic with non-participating lone pair (pyridine) - Lowest: aromatic with delocalized lone pair (pyrrole) **Answer: (B)** ✓