Bromination and Debromination of Cholesterol: An Inquiry-Based Lab Involving Structure Elucidation, Reaction Mechanism, and 1H NMR
Andrew Grant, Devin R. Latimer · Journal of Chemical Education · 2003
A classic laboratory experiment involving the bromination of cholesterol and subsequent zinc-mediated debromination back to cholesterol has been reworked for use in an upper-level organic lab. The emphasis has been changed from the purification of cholesterol to a structure determination, conformation, stereochemistry, and mechanism investigation. A series of instructions and questions designed to help the students deduce the structure and three-dimensional shape of dibromocholesterol from approximate 1 H NMR data has been developed. Dihedral angles from the three-dimensional perspective drawings and the approximate coupling constants gleaned from 1 H NMR data provide the basis for a structural assignment of the dibromocholesterol and allow for a mechanism of bromination to be proposed.