Decarboxylation of THCA in cannabis after plant material is mixed with ethanol [closed]

Question

When making a tincture of cannabis, an early step is decarboxylation by roasting cannabis flowers at low temperatures (such as 230F for 30 minutes). My question is, how can one decarboxylate cannabis that is already in a solution of ethanol?

There are many questions about this online from people who have started making a cannabis tincture but did not decarboxylate the plant matter first. I am asking the question here to learn about this from a chemistry perspective, rather than anecdotes.

Of the anecdotes about this, here are a few ideas which seem credible based on my research on decarboxylation. Which of these processes are safe and effective for decarboxylating cannabis tincture, after the plant matter is mixed with ethanol?

A. "Do nothing": Curing/drying the plant matter first does some decarboxylation, so tinctures made with dried cannabis will likely have psychoactive potency even if not decarboxylated by heat before dissolution.

B. Heat the solution: Given ethanol's boiling point is about 173F, it seems unsafe to heat-by-flame a solution of cannabis and ethanol to decarboxylation temperatures (200-250F). Some suggest using a water bath to apply heat, evaporating the ethanol from an unsealed container in the process, resulting in a concentrated and decarboxylated solution.

C. Dry then heat the plant matter: Cannabis can be filtered out of the solution then left to dry (ethanol evaporating within a day, remaining water taking longer but being of less concern to heat). That relatively-dry and ethanol-free plant matter can then be roasted at low temperatures, as it would be prior to being mixed in a solution for a cannabis tincture. It's unclear to me how well this would work, given cannabinoids and terpenes would already be extracted and remain in the ethanol solution; I expect that after alcohol extraction has begun (e.g. in solution >1 day), decarboxylation of filtered plant matter would be less effective.

Answer 1

Efficient production of tetrahydrocannabinol $(\Delta^9-\mathrm{THC})$ from cannabis is important for its medical application. If that's what your intention is (indicated by studieng the chemistry), you should follow the methods described in two recent patents (Ref.1 & Ref.2):

$\Delta^9$ THC acid is obtained from plant material and extracted into an aqueous solvent under conditions of $\mathrm{pH}$ control. The acid is converted to a salt and the salt extracted into a polar solvent, yielding acid of high purity. The $\Delta^9$ THC acid is then converted to $\Delta^9$ THC which is further purified and combined with a carrier for pharmaceutical use.

I put only the abstract of Ref.1 but recommend to read the whole patent to get better understanding. Also, I'd recommended the reading of Ref.3 for some studieds on decarboxylation and its proposed mechanism.

References:

1. Neil J Goodwin, Nicolas J. Archer, Christopher Murray, Alan K. Greenwood, and Derek McHattie, "Production of $\Delta^9$ tetrahydrocannabinol," United States Patent 2009, US 7,592,468 B2.
2. Frederick R. Ferri, "Method and apparatus for processing herbaceous plant materials including the cannabis plant," United States Patent 2015, US 9,199,960 B2.
3. Helene Perrotin-Brunel, Wim Buijs, Jaap van Spronsen, Maaike J. E. van Roosmalen, Cor J. Peters, Rob Verpoorte, Geert-Jan Witkamp, "Decarboxylation of $\Delta^9$-tetrahydrocannabinol: Kinetics and molecular modeling," Journal of Molecular Structure 2011, 987(1-3), 67–73 (DOI: https://doi.org/10.1016/j.molstruc.2010.11.061)(PDF).