Various quench methods for conversion and isomerization of CBD to Delta 9 THC using AlCl3, and subsequent progressive isomerization of Delta 9 THC to Delta 8

There are many methods for stopping and quenching the simple, effective, and inexpensive method of converting CBD to Delta 9 THC. These methods deactivate the AlCl3 catalyst and the resulting HCl, while also facilitating the transfer of bound Al and acidic residues from the organic layer to the aqueous layer for further purification. These methods include:

  • Using salts:
    KF - very strong Al binding, neutralization of HCl to KCl, and a light oil color.
    K2SO4 - a popular method, but requires multiple rinses. HCl is formed during the reaction, resulting in a rather dark oil color.

  • Using acids:
    H3PO4 - strongly binds Al ions and transfers them to the aqueous layer, resulting in an ideal light oil color, and rapid separation of the layers.
    HCL - an industrial method, requiring several rinses, not producing a perfect color, and slower separation than H3PO4.

  • Using water-soluble bases:
    NaOH - used industrially, but can cause very difficult-to-separate gels and emulsions due to the formation of gelling aluminum hydroxide. Requires huge amounts of water, very risky, and due to its high pH, ​​it produces a dark oil.
    NaHCO3 - also very risky, can cause gels and emulsions that are almost impossible to separate, and is only used on a microscale.

  • The holy grail of quenching, bases that dissolve in and act in the organic layer, rapidly neutralizing AlCl3, HCl, and quenching carbocations—that is, fully inhibiting the mechanisms that cause isomerization, such as:
    TEA - Triethylamine - cheap, effective, and quickly stops the reaction.
    DIPEA - as above, more steric.
    DBU, other strong steric base - stronger than TEA, perhaps immediately removing chlorine attached to some THC-Cl molecules and definitively stopping the ongoing isomerization.

And now a question for the experts:
Have you checked HPLC to see if different quenching methods followed by distillation give different results regarding the conversion of Delta 9 to Delta 8? In theory, despite the presence of THC-Cl, the most strongly quenched reaction and neutralization of carbocations with bases soluble in the organic layer should yield the best result.

If we didn’t use distillation, after evaporating the solvent, obtaining more than 88% Delta 9, often 93-95%, how quickly does the resulting oil convert to Delta 8 at room temperature? Does the quenching method affect this? Has anyone checked whether it takes 1 week, a month, or, for example, six months for the resulting D9 to convert to D8? Or at what ambient temperature, despite quenching, does the oil begin to spontaneously convert to D8?

Has anyone checked the percentage of THC-Cl in the resulting oil, depending on:

  • the amount of AlCl3 catalyst used
  • the amount of DCM used during the reaction
  • the method of quenching the reaction

I don’t have experience with AlCl3 but I have reason to believe the quenching methods touted for removing p-toluene sulfonic acid don’t do shit.

When id run a reaction to convert d9 to d10 if d8 is present almost always the catalyst would be present as well, shifting the d10 yield to d6a10a through the residual acid. This would also shuttle the desirable d8 yield through the reaction due to the presence of the acid, allowing the equilibrium conversion of d8 to d9 and then further shifting the d10 to d6a10a.

I truly believe that d8 and d9 are in equilibrium when d8 is far higher than d9, at all temps. If acid is present I’d imagine the quench is really really important for d9 made with acid. It was really important for making d9 free d8. So d8 free d9 must be a huge pain in the butt.

I don’t have experience obtaining Delta 10, but I once saw a study on the efficient production of Delta 10 by isomerizing CBD with molecular iodine (I2) and quenching the reaction with sodium thiosulfate (Na2S2O3). Thiosulfate deactivates the active iodine into water-soluble iodides and, importantly, significantly impacts the visual appearance of the oil by reducing the colored quinones formed from oxidized CBD, resulting in a beautiful oil color. It’s worth checking out…