See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Analysis of Basicity in Nitrogen Compounds ## Key Principle Basicity depends on the **availability of the lone pair on nitrogen** and its ability to be donated to accept a proton. ## Evaluation of Each Option **(A) Aniline ($C_6H_5NH_2$):** - Lone pair on $N$ is **delocalized** into the aromatic benzene ring - Resonance stabilization reduces electron density at nitrogen - Weakest base **(B) Pyrrole ($C_4H_4NH$):** - Lone pair is **part of the aromatic system** (6 π-electrons) - Highly stabilized; nitrogen is reluctant to donate electrons - Extremely weak base (nearly neutral) **(C) Trimethylamine ($(CH_3)_3N:$):** - Lone pair is **localized** on nitrogen (no delocalization) - Three alkyl groups provide +I inductive effect (electron donation) - Strong base **(D) Triazabicyclo[4.4.0]decane (TBDA) - Guanidine-like structure:** - **Three nitrogen atoms** sharing/stabilizing positive charge when protonated - Lone pair is **highly localized** and available - The bicyclic structure rigidly positions lone pairs for donation - Protonation creates a **resonance-stabilized cationic** intermediate with charge distributed across multiple $N$ atoms - **Strongest base** ## Conclusion **Option (D)** is the strongest base because it combines localized lone pairs with exceptional stabilization of the conjugate acid through multi-center resonance, making proton acceptance highly favorable.