Regarding 'oiling out'

[benzyme]

We've all seen it, a clear (sometimes yellowish/orange) residue that doesn't resolve. It's frustrating. Sometimes it is due to impurities, but often it's simply a supersaturated solution of unresolved polymorphs. I've recently applied a couple effective strategies to resolve it. One involves adding ethyl acetate, with a glass dropper. I add just a few drops, swirl it around, and pour into another clean flask. As it evaporates, it usually leaves behind clear crystals, which are suitable for seeding.
Another effective strategy is adding a small amount of boiling methanol. Since methanol has a lower boiling point and is more polar, it will spontaneously cause dmt freebase to crystallize.

To determine whether or not you may have dimers/polymers in your extract, isolate a small sample and illuminate it with a 365nm blacklight. DMT should glow light blue, dimers will glow orange. This is due to a larger Stokes shift, there are more pi-bonds (double-bonds), so the emission wavelength is longer.

 

[Icon]

Polymorphism is an inherent property of the molecule, due to partially-rotatable alpha and beta carbons; solvents influence the orientation, but the variability already exists.

So while it's still a liquid, the molecules are still rotating and indistinguishable, right? Which means they can't be described as one polymorph or another. After the molecules settle into a stable lattice and stop rotating, forming a solid, then it's a mixture of polymorph(s).

The way you've been describing it makes it sound like any oiling out is caused by polymorphism in solution. Isomorphic substances can also oil out when local microclimates in the solvent achieve a high enough supersaturation.

It's not just about solvent selection either, it's ultimately about molecular kinetics. A solvent with low-solubility will certainly help by increasing the threshold for conditions, but you can still oil-out DMT in hexane if you put it straight in the freezer from saturated room temp.

Even a saturated hexane solution left at room temp can oil out. If the diffusion kinetics are outpaced by growing crystals, spheres of depleted solvent around the crystals form. In a still solution, the depleted sphere builds up a positive pressure, from the crystal displacing volume. This lowers solute solubility in the sphere, further slowing growth and further building up solute molecules at the edge of the sphere. There's not enough energy to nucleate, so the band of high concentration separates into a liquid instead.

 

[benzyme]

The way you've been describing it makes it sound like any oiling out is caused by polymorphism.

No, that's not what I'm suggesting at all. I'm suggesting it is caused by supersolubility.

Isomorphic substances can also oil out when local microclimates in the solvent achieve a high enough supersaturation.

How do you figure? If is was isomorphic, it would form a lattice. That is the point of recrystallization, exceeding solubility equilibrium. We're also trying to eliminate all solvent, or it will still have a residual solution present. Even with an x-ray crystallography instrument, we wouldn't be able to ascertain the morphology in said supersaturated solution.

It's not just about solvent selection either, it's ultimately about molecular kinetics. A solvent with low-solubility will certainly help by increasing the threshold for conditions, but you can still oil-out DMT in hexane if you put it straight in the freezer from saturated room temp.

solvent selection and temperature. logP is just as important here as temperatures. Any other residual solvents (like ethyl acetate) with higher boiling points will likely result in it oiling out, depending on the ratio. Assuming the residue contains no/minimal residual solvent, it will crash out with boiling hexane, upon cooling. methylene chloride has a similar boiling point, but its logp is close to dmt. it usually leaves a residue.

You're really overthinking this, and getting caught up in semantics. I posted this thread as a means of troubleshooting, not a discourse in solubility equilibria. Maybe I should have titled it "regarding the residue" instead. I only mention polymorphs, because I've also seen a wide range of different melting points ranges from crystals from various recrystallization solvents. What the "oil" is, is a supersaturated solution. The residue is a mixture of unresolved polymorphs.

 

[GreaseBall]

We've all seen it, a clear (sometimes yellowish/orange) residue that doesn't resolve. It's frustrating. Sometimes it is due to impurities, but often it's simply a supersaturated solution of unresolved polymorphs. I've recently applied a couple effective strategies to resolve it. One involves adding ethyl acetate, with a glass dropper. I add just a few drops, swirl it around, and pour into another clean flask. As it evaporates, it usually leaves behind clear crystals, which are suitable for seeding.
Another effective strategy is adding a small amount of boiling methanol. Since methanol has a lower boiling point and is more polar, it will spontaneously cause dmt freebase to crystallize.

To determine whether or not you may have dimers/polymers in your extract, isolate a small sample and illuminate it with a 365nm blacklight. DMT should glow light blue, dimers will glow orange. This is due to a larger Stokes shift, there are more pi-bonds (double-bonds), so the emission wavelength is longer.

what do you mean by unresolved polymorphs? isnt it just waxes and fats from the plant material? does the contaminate residue act as a solvent and trap the DMT in its goopiness instead of crystallizing?

 

[benzyme]

what do you mean by unresolved polymorphs? isnt it just waxes and fats from the plant material? does the contaminate residue act as a solvent and trap the DMT in its goopiness instead of crystallizing?

Not necessarily; what I'm describing also occurs in synthetic. In both cases, what I described is an issue of residual solvent and supersaturation.

 

[benzyme]

For some reason, people tend to associate a residue and orange color to "plant fats". Fats (lipids) are fatty acids, which upon basification, are hydrolized into soap (saponification). Most of this appears as a layer between the nonpolar and polar phases. If it's a concern, it's resolved by washing the nonpolar solvent with brine, and then drying the nonpolar over sodium (or magnesium) sulfate.
The color has nothing to do with other impurities. Many tryptamines tend to turn tan or orange.