Exploration of solvent effects on the transition state of Grignard exchange reactions

Abstract

Transition state energies for many reactions fluctuate with the particular solvent that the reaction runs in. Although fluctuations are suspected for the halogen-magnesium exchange reaction, computational validation of solvent effects on transition states for this reaction remains unexplored. Determination of the best solvent for the exchange reaction can lead to more controlled reactions involving the Grignard reagent. Diethyl ether, a widely used coordinating solvent in organomagnesium chemistry, stabilizes Grignard reagents. We considered a well established exchange reaction between isopropyl magnesium chloride and 4-chlorobenzonitrile. We explored 0,1, or 2 diethyl ether molecules in coordination with the magnesium throughout the reaction from reactants to products using the wB97X-D4//cc-pVTZ level of theory and implicit solvent in GAMESS. We determined the best arrangement of solvent in the transition state and discuss the promise of using these calculations for alternate solvents.