See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Determining the Nonplanar Cation **Step 1: Analyze the geometry of each cation** For a cation to be **nonplanar**, the central atom must have **tetrahedral or pyramidal geometry** (3D structure), not trigonal planar or linear. **Step 2: Examine each option** **(A) $NH_4^+$ (Ammonium ion)** - Central atom: N with 4 bonding pairs (4 H atoms) - Hybridization: $sp^3$ - Geometry: **Tetrahedral** → **Nonplanar** ✓ **(B) $CH_3^+$ (Methyl cation)** - Central atom: C with 3 bonding pairs - Hybridization: $sp^2$ - Geometry: **Trigonal planar** → Planar ✗ **(C) $CH_3CO^+$ (Acetylium ion)** - The $CO$ part has a C triple-bonded to O (linear) - Overall structure: **Planar** ✗ **(D) $(CH_3)_3C^+SbF_6^-$ (Trityl cation)** - Central C has 3 C-C bonds in trigonal planar arrangement - Geometry: **Trigonal planar** → Planar ✗ **Answer: (A) $NH_4^+$** $NH_4^+$ is the only cation with tetrahedral geometry around the central nitrogen atom, making it inherently **nonplanar** in 3D space.