Investigating the regioselective enolization of 2-substituted cyclohexanones: A green chemistry experiment for organic labs

Steven Paul Lee, School of Science and Mathematics, School of Science and Mathematics, Roosevelt University, 1400 N. Roosevelt Boulevard, Albert A. Robin Campus, Schaumburg, IL 60173

Power Point Presentation (PDF)

ABSTRACT: This green organic laboratory experiment examines the regioselectivity of kinetic vs. thermodynamic control in a mini-research project. In this experiment, students react 2-substituted cyclohexanones with a silylating agent (e.g. BSA or BSTFA) in an ionic solvent or without solvent to produce silyl enol ethers. Students start with 2-substituted cyclohexanones with different substituents (alkyl groups and heteroatoms) to prepare the corresponding silyl enol ether products, and determine the product ratios by GC and NMR. Then the students share their data and work together to explain trends in regioselectivities of the enolizations. This experiment involves green chemistry, ionic solvents, and thermodynamic and kinetic control of enolization. The lab is based upon a recent literature report (Org. Lett. 2001, 3, 1037-1039), but explores additional cyclohexanone substrates and silylating procedures.