What happens when you smoke a pre-roll?

Smoking a cannabis preroll triggers a complex series of chemical reactions driven by heat, primarily categorized into decarboxylation, pyrolysis, and synthesis. In its raw form, cannabis contains non-psychoactive cannabinoid acids, such as tetrahydrocannabinolic acid (THCA) and cannabidiolic acid (CBDA). When the preroll is ignited, the high temperature removes a carboxyl group from these molecules in a process called decarboxylation. This reaction instantly transforms THCA into active delta-9-tetrahydrocannabinol (\(\Delta ^{9}\)-THC), the compound responsible for the psychotropic effects, and CBDA into cannabidiol (CBD).

As the cannabis burns, the material behind the cherry (the lit tip) reaches temperatures ranging from 600°C to over 900°C. This extreme heat causes pyrolysis, which is the thermal decomposition of organic matter in the absence of sufficient oxygen. Pyrolysis breaks down complex plant cells, cellulose, and lipids into smaller, volatile fragments. While many aromatic terpenes—the compounds that give cannabis its distinct smell and flavor—are vaporized intact just ahead of the burn zone, others are destroyed or chemically altered by the intense heat, creating new flavor profiles and byproducts.