See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Weakest Base Among Amino Compounds **Analysis of each option:** **(A) Pyrrolidine (5-membered ring with NH)** - Secondary amine with sp³ hybridized N - Lone pair on N is readily available - Moderate basicity **(B) Piperazine (6-membered ring with two NH)** - Two secondary amines in the ring - Both nitrogens share electron density through inductive effects - Each N donates electrons to stabilize the other's lone pair - This **delocalizes** the basicity, making lone pairs less available for protonation - **Weakest base** **(C) Cyclohexylamine (primary amine)** - Primary amine with sp³ hybridized N and one lone pair - Electron-donating alkyl group increases basicity - Strong base **(D) Pyridine (aromatic heterocycle)** - Aromatic N with sp² hybridization - Lone pair is in-plane and less available due to aromatic stabilization - Moderate basicity (weaker than aliphatic amines) **Why B is weakest:** The two N atoms in piperazine are **electronically equivalent** and interact with each other. Each nitrogen's lone pair is partially donated to stabilize the adjacent nitrogen through resonance-like orbital overlap. This **reduces the electron density** available on each nitrogen for accepting a proton, making piperazine significantly weaker than all other options. **Answer: (B)**