// Definition
The length of the alkyl side chain at the C3 position of cannabinoid molecules, which directly influences receptor binding affinity and psychoactivity. Pentyl (5C) chains are standard in THC/CBD, propyl (3C) in THCV/CBDV, and heptyl (7C) in THCP.
// From the Episode
Chimera explained the structure clearly: THC/CBD have a five-carbon pentyl tail, propyl variants (THCV) have a shortened three-carbon tail, and THCP has an extended seven-carbon tail. He stated that 'the length of the tail is proportional to the psychoactivity of the molecule.' Dr. Mark added that the CB1 receptor has 'hydrophobic promiscuity' that can accommodate larger carbon chains, and that the X-ray crystal structure of CB1 was solved with a synthetic cannabinoid docked in the active site.