Known methods
Phytocannabinoids exist like precursors to their pharmacologically active counterparts. [12] [13] At least three independent methods have successfully converted CBD to THC.
- Despite the CBD and THC having the same molecular weight, multiple analytical methods are able to differentiate them. [12]
- "on the recovery of both THC (86.7−90.0%) and CBD (92.3−95.6%). The slightly lower recovery of THC can be explained by the fact that THC is less polar than CBD and more likely to remain in the nonpolar sunflower oil." [12]
By heat
CBD heated to 175, [14] or 250–300 °C may partially be converted into THC. [15] Even at room temperature, trace amounts of THC can be formed as a contaminant in CBD stored for long periods in the presence of moisture and carbon dioxide in the air, with storage under inert gas required to maintain analytically pure CBD. [16]
- Heat is required to decarboxylate the non-psychoactive phytocannabinoid THCA to its psychoactive form, THC. Likewise, CBDA turns into CBD.
- From hemp plant material in an oven, cannabinoid concentration plots (time/temp) show THC: [17]
- STP 0 minutes 0.20 mg/g
- 140-160C 20 minutes 0.27 mg/g
- 140-160C 60 minutes 0.05-0.15 mg/g
- 120C 45 minutes 0.27 mg/g
- 120C 90 minutes 0.20 mg/g
- 100C 90 minutes 0.25 mg/g
- 80C 120 minutes 0.24 mg/g
Multiple oxidation products form during degradation in the presence of oxygen, a process known as thermolysis In contrast, the absence of oxygen leads to a process called pyrolysis which significantly reduces the loss.
- "...the boiling point for THC has been determined at 157 °C, and the boiling point range for CBD sits between 160 and 180 °C." [17]
With acid
CBD converts to various isomers of THC with catalysts in acidic environments. [18] A wide variety of acids can be used, though different conditions result in varying yield and formation of characteristic impurities. [19] [20] [21] [22]
- Catalytic acid solution in 5 minutes in a microwave oven with a 40% THC (Δ9-THC) and 35% Δ-8-Tetrahydrocannabinol yield. [23]
- Adding protons until the CBD sterically-hindered alcohol functional group cyclises to the pyran ring of THC. [24]
- Lewis acids. [25] - a continuous rather than batch implementation with similar materials [9]
- Gaoni and Mechoulam [26] also described a method for converting CBD to Δ9-THC comprising refluxing a mixture of CBD in ethanol containing 0.05% hydrogen chloride for 2 hours. Percentage yield of Δ9-THC (Δ1-THC) was 2%. [27] [28] Using boron trifluoride, the yield was 70% [29] although purity was not given. [30]
With zeolite
Methods have been claimed for converting CBD to a mixture of Δ8-THC and Δ9-THC using "Zeolites selected from the group consisting of analcime, chabazite, clinoptilolite, erionite, mordenite, phillipsite, and ferrierite." [31]
