In gaseous triethylamine the “-C-N-C-“ bond angle is ________ degree. — Amines Chemistry Question

💡 Solution & Explanation

**Step 1: Determine the molecular geometry around nitrogen.** In triethylamine (Et₃N), nitrogen is the central atom bonded to three ethyl groups (-C₂H₅). Nitrogen has 5 valence electrons: 3 are used for bonding with carbon atoms, and 2 form a lone pair. **Step 2: Apply VSEPR theory.** Around nitrogen: - 3 bonding pairs (C-N bonds) - 1 lone pair - Total: 4 electron pairs **Step 3: Determine electron geometry and molecular geometry.** With 4 electron pairs, the electron geometry is tetrahedral. With 3 bonding pairs and 1 lone pair, the molecular geometry around N is **trigonal pyramidal**. **Step 4: Identify the ideal tetrahedral angle.** In a tetrahedral arrangement, ideal bond angles = 109.5° **Step 5: Account for lone pair repulsion.** Lone pairs repel more strongly than bonding pairs, compressing the C-N-C bond angles slightly below the tetrahedral angle. However, in gaseous triethylamine, experimental measurements show the bond angles are approximately 108°, reflecting the geometry of a slightly compressed tetrahedron. **Step 6: State the C-N-C bond angle.** The -C-N-C- bond angle in gaseous triethylamine is close to the tetrahedral angle with slight compression. Therefore, the answer is **108.00** degrees.