The Zimmerman-Traxler model is invoked to rationalize the unexpected stereochemical outcomes of certain aldol reactions, such as the Reformatsky and Ivanov reactions. It models the stereochemistry of the products, based on the steric hindrance in the possible six-membered transition states in the aldol condensation reactions. Created by Alexis Johnson (Undergraduate) Edited by Margaret Hilton Honors Organic Chemistry CHEM 2321 (Sigman), 2013, University of Utah