The techniques described here require at least High School chemistry lab training and experience in chemistry lab techniques, as well as adequate ventilation and personal protection gear.

Acetic Anhydride is both highly corrosive and about as flammable as gasoline, with a lower explosive limit of 2.7% and an upper of 10.3%.  Hexane is also about as flammable as gasoline and has an LEL of about 1.15% and an UEL of 7.5%.

In addition, Sulfuric Acid (H2SO4) is also highly corrosive, though not flammable.

Do not attempt any of these techniques if you don’t have the proper training and equipment, including the MSDS sheets for all the chemicals involved.

We provide this as information only and neither recommend this procedure, or accept responsibility if you experiment with it yourself. 

The term isomerizing this case, means turning CBD into one of its Delta 8 or 9 THC isomers.  

According to D Gold, the credits for discovering the reaction goes to Roger Adams in about 1940, but wasn’t truly refined until the 1960’s. 

Sweet Mary produces CBG as a precursor to both CBD and THC, and then decides which one to turn it into.  In the original land race strains, she leaned more heavily toward CBD production, and total oil production from land race plants is relatively low.

Enter the recreational growers, whom selectively bred for not only more THC percentage than CBD, but also keeping the higher total essential oil production previously bred into recreational strains.

Act three, enter medical cannabis, and suddenly interest in CBD is elevated, so the selective breeding turned to producing phenotypes producing both high CBD and high oil production.

Now there is a panoply of choices of not only high THC or CBD, but a variety of phenotypes with varying percentages of both, interest in isomerizing is less intense, but still present, so here is our experience with it. 

I first stumbled across it reading Cannabis Alchemy by D Gold, and Marujuana Chemistry by Michael Starks, both written in the 1970’s, when CBD levels were higher, and when a method to turn CBD to THC was coveted and golden.

Isomerizing is accomplished by reflux boiling a solution of a winterized CBD rich essential oil in a solvent, to which acid is added.  The reaction involves forming a third ring by adding an oxygen, and shifting the double bond from position 1,2, to position 6,1.

They both make the point that the production between predominantly Delta 8 and 9 THC production from CBD, is the the process.  Milder acids and shorter reflux times produce predominantly Delta 9 THC, while stronger acids and longer reflux times produce predominantly Delta 8. 

As we’uns were most interested in the higher rotating form of Delta 9, vis a vis 8, we decided to try a milder process.

Sadly at that time, we had limited access to high CBD material, and highly coveted what we did have, soooo decided to isomerize some material with less than 5% CBD, to see if it improved the head effects.

 We started by dissolving some BHO into 200 proof ethanol at about a 10:1 ratio and sticking it in a -18C/0F freezer for 48 hours to precipitate out the plant waxes.  

We vacuum filtered that solution to about 15 microns using a #1 lab filter, but it can also be done using gravity and a coffee filter.  

We then poured the  filtered solution into a flat bottomed 1 liter boiling flask with tapered neck and dropped in a 3/4″ stir bar, and set the flask on a stirring hotplate set at 82C/180F. 

We slowly added a drop of sulfuric acid (H2SO4) per gram of oil while stirring at medium speed, and then reduced stir speed to slow and installed a Alihn refluxing condenser into the tapered neck of the boiling flask.  

We started the cooling pump, which circulated ice water through the Alihn and once the solution started boiling, adjusted the temperature to a low simmer.  The vapors should rise only halfway up the condenser, before being condensed back to a liquid and rain falling back to the boiling flask.

1 Liter boiling flask with Alihn refluxing condensor on Thermodyne stirring hotplate.

Stirring and refluxing

 After two hours of reflux boiling, we removed the solution from the hot plate, and set the condenser aside.

We poured the solution into a 1 liter seperatory funnel, to which we added an equal volume of HPLC Reagent grade n-Hexane.


 And then added about four times as much water, before shaking well and then allowing to settle out:

Adding about 4 times as much water as solution.

Shake well, while holding the stopper and petcock in place.

Separated solution ready to bleed off the alcohol water solution on the bottom.

 Next we add about four volumes of a 5% bicarbonate of soda solution and again shake well, before allowing to settle, and then draining off the bicarbonate solution.

We then twice add about four volumes of clear water, shake, settle and drain off the water.  At this point the water solution at the bottom should be clear after settling.

We just evaporated off the hexane, but it can also be removed using a rotovape, or by other means.

What we ended up with was a stringy material darker than the starting absolute.

 Isomerized on the left, starting Absolute on the right.

The pockmarks are from taking samples and the specks in the one on the right are fruit flies, whom fell in love with the aroma when we forgot to cover it as it cooled. 

 Isomerized Absolute

That leads us to effects, and sadly the less than 5% increase in THC was not captivating, bringing us back to the subject of starting material.  If you want to see more improvement, start with material that has higher CBD……………..

If’n ya’ll decide to try this yourself, I recommend the following safety gear:

Chemical goggles

Respirator with acid cartridge

Chemical apron

Chemical gloves

Adequate ventillation

Fire extinguisher

Bicarbonate of soda for neutralizing any spills

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