See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# R/S Configuration Analysis To determine 'S' configuration, apply the **CIP (Cahn-Ingold-Prelog) rules**: ## Option (D): $H_2N-\overset{*}{C}(COOH)(H)-CH_3$ **Step 1: Identify the stereocenter** The central carbon (marked *) is bonded to: $-NH_2$, $-COOH$, $-H$, $-CH_3$ **Step 2: Assign priorities (1-4) by atomic number** | Group | Atoms bonded to central C | Priority | |-------|---------------------------|----------| | $-NH_2$ | N(7) | **1** (highest atomic #) | | $-COOH$ | C bonded to O,O,C | **2** (O > H,C) | | $-CH_3$ | C bonded to H,H,H | **3** (only H atoms) | | $-H$ | H(1) | **4** (lowest atomic #) | **Step 3: Orient and trace** Place the 4 group away from you. Trace the path $1 \rightarrow 2 \rightarrow 3$: - From $NH_2$ → $COOH$ → $CH_3$ proceeds in **counterclockwise direction** **Step 4: Assign configuration** Counterclockwise = **S configuration** ✓ **Why others fail:** Options (A), (B), and (C) either lack a proper stereocenter or have four identical groups at the stereocenter.