10.1.1 Decarboxylation of Tetrahydrocannabinolic acid (THCA) to active THC
by Iffland, Carus, Grotenhermen, at nova-Institute GmbH
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This study found that the highest THC content was achieved at 145C in 7 minutes, but by 40 minutes the total THC was reduced by 50%.
Some key quotes paraphrased:
Based on the trend line, it would take about 3 hours at 100 °C to fully convert THCA into THC and about 4 hours at 98 °C. Temperatures above 160 °C require only about 10 minutes, and only seconds are needed to convert THCA fully into THC at 200C.
Side reactions altering total THC levels achieved:
THC evaporates starting around 157 °C THC , so the peak THC levels presented, are only present for a snapshot in time.
In this study, the highest THC content was reached after 7 minutes at 145 °C , and the total THC amount was already halved after 40 minutes (Veress et al., 1990). Taschwer and colleagues
(2015) reported peak THC levels after 3 min at 150 °C, and approaching zero remaining THC percentages after 7 min.
Figure 1: Decarboxylation reaction of THCA to THC (adapted from Perrotin-Brunel et al., 201
Complete Decarboxylation graph
Besides THC evaporation, there are several other reactions that occur at different temperatures. IE:, Dussy et al, were only able to achieve maximum of 70% THC from 100% THCA.
Polymerization and oxidation of THCA and THC to CBN and CBNA, respectively, are given as side reactions, accounting for this difference. THC degradation to CBN can can be significant between 85 –100 °C (Repka et al., 2006).
The THCA decarboxylation reaction starts at 90 °C (Veress et al., 1990; Peschel, 2010).
Here is a graph based on a study by the Institute of Legal Medicine showing a similar curve at 70% decarboxylation.