Delta 9 THC is the naturally occurring form of THC found in natural marijuana flower. Delta 8 THC is not a natural occurring isomer in cannabis flower and I have only observed its presence in distillate that was purposely manufactured to contain it or even sometimes where it was an un-intentional product in the distillate manufacturing process where due to a mix of delta 9 and delta 8. Chemically, the only difference between both of these isomers is the placement of the double bond on the THC molecule. However, slight differences in chemical composition can have significantly different psychoactive effects. Due to these differences, labs do not typically include delta8-THC in their total available THC figures and only list it under “other cannabinoids” with the designation of delta-8 THC.
The NIH National Cancer Institute defines Delta 8 THC as “An analogue of tetrahydrocannabinol (THC) with antiemetic, anxiolytic, appetite-stimulating, analgesic, and neuroprotective properties. Delta-8-tetrahydrocannabinol (delta-8-THC) binds to the cannabinoid G-protein coupled receptor CB1, located in the central nervous system; CB1 receptor activation inhibits adenyl cyclase, increases mitogen-activated protein kinase activities, modulates several potassium channel conductances and inhibits N- and P/Q-type Ca2+ channels. This agent exhibits a lower psychotropic potency than delta-9-tetrahydrocannabinol (delta-9-THC), the primary form of THC found in cannabis.”
There are companies that purposefully manufacture delta 8 THC distillates. It has been purported that delta 8 THC has milder psychoactive effects and works better as anti-nausea product for cancer patients whereas delta 9 might cause unwanted psychoactive side effects to those same cancer patients. However, there is little peer reviewed research into the effects of delta 8 THC compared to delta 9 THC.
The next question is how is delta 8 THC extracted or produced? Companies that manufacture products high in delta 8 THC don’t explain their manufacturing process however there are known synthetic steps to isomerize delta 9 THC to delta 8 THC.
One way to isomerize delta 9 THC into delta 8 THC is to heat it in an acidic condition such as the condition present when derivitizing delta 9 THC for GC analysis (source). It has been proposed that other acidic environments can be used to isomerize delta 9 THC to delta 8 THC. This isomerization can happen intentionally or unintentionally. I have read comments in online forums such as Reddit where THC concentrate manufacturers were surprised when lab results came back with abnormally high concentrations of delta 8 THC. I have seen a potency value for distillate in a vape cartridge that not only had predominantly delta 8 THC, but also did not come near the advertised THC concentration. The use of bleaching clays, which are mildly acidic in nature, in the concentrate extraction process could be responsible for this conversion. The reason behind this is that the delta 8 form of THC is more thermodynamically stable than the delta 9 form. This is similar to how CBN is more stable than delta 9 THC due to its conjugated structure and the reason why you see high CBN content in older THC products that have undergone oxidative degradation, but that is a separate topic on its own.
Another way to create delta 8 THC is through the isomerization of CBD to delta 9 THC and from delta 9 THC to delta 8 THC. CBD and THC are also isomers of each other meaning that they possess the same chemical formula but the atoms are arranged differently. There is a patent describing this process under certain heated and acidic conditions.