See image — Haloalkanes and Haloarenes Chemistry Question

💡 Solution & Explanation

Concept: SN2 reactions proceed with inversion of configuration (Walden inversion) at the carbon bearing the leaving group. Step 1 - Identify the substrate configuration: The starting material is a cyclohexane ring with Br on a wedge bond at C1 (coming toward the viewer) and H on a dash bond at C1 (going away), and CH3 on a wedge at C4 with H on a dash at C4. The two substituents (Br and CH3) being on wedge bonds at opposite ends of the ring indicates they are trans to each other (trans-1-bromo-4-methylcyclohexane). Step 2 - Apply SN2 mechanism: In SN2, the nucleophile (OH-) attacks from the back side (anti to the leaving group Br). Since Br is on the wedge (front face) at C1, OH- attacks from the back (dash side). This means OH ends up on the dash bond at C1, while H remains on the wedge bond at C1. Step 3 - Identify the product structure: After inversion at C1: H is now on the wedge at C1, and OH is on the dash at C1. The CH3 group at C4 remains unchanged (wedge). This matches option (b): H on wedge at C1, HO on dash at C1, CH3 on wedge at C4, H on dash at C4. Step 4 - Why option (a) is wrong: Option (a) shows HO on the wedge at C1 (same face as Br was), which would represent retention of configuration. SN2 never proceeds with retention; it always gives inversion. So (a) is incorrect. Step 5 - Why options (c) and (d) are wrong: Since only inversion occurs in SN2, only one stereochemical outcome is possible, ruling out (c). The product does exist and matches (b), ruling out (d). Therefore, the correct answer is B.