Many cannabinoids can convert into each other—after all, cannabidiolic acid (CBDA), tetrahydrocannabinolic acid (THCA), and cannabichromenic acid (CBCA) stem from the same origin, cannabigerolic acid (CBGA), “the mother of cannabinoids.”
Converting prominent cannabinoids that are relatively abundant in cannabis into more obscure, scarce, but valuable ones through synthesis—chemical or bio—is a viable “cheat” code to produce sufficient amounts of these rare cannabinoids in a time- and cost-efficient manner.
In that spirit, a group of scientists including Raphael Mechoulam came up with a way to convert CBD into delta-8-THC (Δ8-THC ) or delta-9-THC (Δ9-THC) through chemical synthesis. They patented their process (through 2022) with the United States as patent US20040143126A1. The patent provides a basic outline:
- Mix a Lewis acid in an organic solvent
- Add CBD
- Reflux the mixture
- Dilute with an organic solvent
- Pour into cold water
- Let the mixture separate into aqueous and organic phase
- Remove organic phase (the phase with the Δ8-THC)
- Elute Δ8-THC
To achieve conversion into Δ8-THC, they added 300 mg of CBD to dried p-toluenesulfonic acid (30 mg) in toluene (15 ml), under N2 atmosphere (inert and free of oxygen). This was refluxed for one hour (superior to other times tested, including 30 minutes and two hours). The p-toluenesulfonic acid served as the catalyst. That said, other Lewis acids may be used, such as boron trifluoride. The mixture was diluted with 20 ml of ether and poured into cold water.
“The upper layer was separated, washed with aqueous 5% NaHCO3 [sodium bicarbonate], then with water, dried over MgSO [magnesium sulfate] and evaporated.”
High-performance liquid chromatography (HPLC) revealed 86% purity of Δ8-THC. The scientists note N2 atmosphere “does not appear as necessary as during the conversion of CBD to Δ9-THC. Besides toluene, other solvents, like benzene, can be used,” but not with the same efficacy, at least according to their tests.
It may be simpler to convert Δ9-THC to Δ8-THC. BR Instruments advises a spinning band distillation system with 4% acidic alumina silicate mixed into crude cannabis oil, noting that this “catalyze[s] the rearrangement of the THC molecule from delta-9 to delta-8-THC.”