Re-Examining Cannabidiol: Conversion to Tetrahydrocannabinol Using Only Heat

Introduction: In the last decade, the market for Cannabidiol (CBD) has grown to become a near $2 billion dollar industry in the United States alone. This growth can be attributed to a growing social acceptance of marijuana, a more detailed understanding of many health benefits attributed to cannabinoids, and the low cost and wide availibility of hemp-derived cannabinoids. Due to the complex legal histories of marijuana and cannabinoids, the stability and safety of CBD is still an area of interest as research has been restricted globally. Conversion of CBD to its psychoactive isomers, most notably delta-9-Tetrahydrocannabinol (Δ9-THC), presents a significant safety issue for consumers and producers of CBD products. Methods: Previous studies investigating the stability of CBD have focused mainly on replicating conditions experienced during long-term storage at room temperature or lower. Here, we report the thermal stability of CBD at 175°C. Dynamic ¹H-NMR experiments and computational electronic structure calculations were used to characterize possible reaction paths from CBD to THC. Results: After 30 minutes of heating, Δ9-THC was produced in detectable amounts in aerobic and anaerobic conditions without an acid catalyst. Conclusions: Our findings support an energetically feasible reaction route that is favorable due to both an increase in phenol acidity at high temperatures and the presence of intramolecular OH-π hydrogen bonding.