In a 2D Fischer Projection, horizontal lines represent bonds projecting outward toward the viewer. I — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

Horizontal lines on a Fischer projection indicate the substituent is pointing straight out at the observer. The rigid shortcut for this scenario is to trace the $1 \rightarrow 2 \rightarrow 3$ path, observe the apparent direction, and reverse it. An apparent clockwise (R) trace dictates that the true configuration is 'S'.