Conversion of CBD to THC

[14] 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.

[17] A wide variety of acids can be used, though different conditions result in varying yield and formation of characteristic impurities.

[18][19][20][21] 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.

There is a debated hypothesis that oral CBD could be metabolized into THC under acidic conditions in the stomach and then absorbed into the bloodstream.

[20] The conversion of CBD to THC by an acid based cyclization reaction was first patented by Roger Adams in the 1940s.