See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Basicity of Amines in Gaseous State **Key Concept:** Basicity depends on the availability of the lone pair on nitrogen. In the gaseous state, steric effects dominate (no solvation to stabilize cations). ## Analysis: **Primary amines ($1°$):** One alkyl group + two H atoms - Lone pair on N is relatively unhindered - Can form stable conjugate acid **Secondary amines ($2°$):** Two alkyl groups + one H atom - Lone pair slightly more hindered than primary - Good basicity **Tertiary amines ($3°$):** Three alkyl groups + no H atoms - Lone pair most hindered by bulky alkyl groups - **However**, the conjugate acid cannot be solvated effectively in gaseous state - Cannot form intramolecular hydrogen bonding - Less stable cation in gas phase **Ammonia ($NH_3$):** No alkyl groups - Lone pair completely unhindered - Forms very stable conjugate acid $NH_4^+$ ## Order in Gaseous State: $$3° > 2° > 1° > NH_3$$ In gaseous state, steric hindrance in forming the conjugate acid becomes paramount. Tertiary amines are most basic because the three electron-donating alkyl groups enhance the basicity of the lone pair through the **inductive effect**, despite increased steric bulk. **Answer: (C) $3° > 2° > 1° > NH_3$**