Resumen de Isolation and Structure Elucidation of the Terpene β-Thujone from Cedar Leaf Oil
Western red cedar leaf affords an essential oil characterized by high thujone content. Students in an advanced organic chemistry lab course isolate a single thujone diastereoisomer from commercially available cedar leaf oil. Treatment of crude oil, containing roughly 70% thujone, predominately as α-thujone (6.5:1), with ethanolic sodium hydroxide leads to epimerization at the chiral α-carbon. Equilibration thus inverts the diastereoisomeric ratio in favor (roughly 2:1) of the β-thujone epimer. Selective formation of the bisulfite addition product from the β-isomer allows for a simple purification via filtration. Release of the free ketone upon treatment with Na2CO3 yields highly pure β-thujone, which is characterized and identified using IR, MS, and NMR spectroscopy.
