But THC and CBD are hardly present in cannabis when the plant is rooted and growing.
When the plant produces cannabinoids, they initially appear in their “acid” forms. Acid cannabinoids are sometimes referred to as “raw” cannabinoids. In the case of THC and CBD, these raw cannabinoids are tetrahydrocannabinolic acid (THCA) and cannabidiolic acid (CBDA), respectively.
What makes THC different from THCA — and CBD different from CBDA — hinges on a process known as “decarboxylation,” aka “decarbing,” whereby raw cannabis is heated so that the chemical structure of the acid cannabinoids changes to a neutral (non-acid) form. THC and CBD are the neutral forms of THCA and CBDA.
The major difference, chemically, between acid cannabinoids and their neutral counterparts is an extra -COOH bond, known as a “carboxyl” group, which consists of a carbon-oxygen-oxygen-hydrogen molecular cluster. In order to transform cannabinoids acids into their neutral forms, they need to go through a process that removes the carboxyl group. This process is referred to as decarboxylation.
As it turns out, the bond holding the carboxyl group in place is pretty weak and easily broken by a combination of heat and time. Decarboxylation is what happens when the carboxyl group is shed due to high temperature or combustion.