Guide to Stereochemistry Concepts and Analysis of Reaction Stereochemistry as Applied to Electrophilic Addition

Step 1. Start at the first atom of the group attached directly to the chiral carbon: the higher atomic number has the higher priority.

Step 2. If the directly connected atoms of two or more different groups are the same atom this is a tie. To break the tie at the first point of difference: begin comparing, one at a time, all atoms attached to the equivalent connecting atoms until a difference is found. a. Always begin by comparing the higher atomic number atoms

on each equivalent connecting atom first. b. Be sure to compare all atoms attached to the equivalent con-

necting atoms to find a difference before moving down the substituent chain.