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Dry Ice and Acetone Freeze Precipitation

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Has anyone used a dry ice and acetone bath to speed up freeze precipitation? Since its much colder it should allow more dmt to precipitate out at a given saturation. I have found it time consuming to reduce my naptha solution so I am hoping this would work well.
 
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Yeah I've done it with naphta. A small little freezer, dry ice at the bottom, ice on top; pyrex dish with DMT-naphta sitting on top; works OK, but a freezer is better and dry ice is expensive.
 
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FranLover said:
Yeah I've done it with naphta. A small little freezer, dry ice at the bottom, ice on top; pyrex dish with DMT-naphta sitting on top; works OK, but a freezer is better and dry ice is expensive.
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Well I failed to recognize just how cold acetone and dry ice is upon reacting. Completely froze the naptha! Ended up putting it in the freezer as per usual. I think slowly precipitating it out is also important. Makes decanting off the naptha much easier since solid crystals will form.
 
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dry ice baths aren't really optimal for recrystallization, since the temperature change is far too dramatic, or not easily controlled for slow crystallization. As a result, you get fine crystals or precipitate, or worse, an oil that falls out and solidifies. Even the escaping CO2 bubbles in the dry ice bath are enough to disturb the flask and interfere with crystal growth.

Naphtha is also not the best solvent for freeze precipitation, its better to use hexanes. the tryptamines are more soluble in naphtha at low temperatures, and as it contains high boiling/low melting hydrocarbons, so it's not suitable for temperatures as low as -78C.

In this case, -20C with hexanes is plenty cold to induce complete crystallization, and in the freezer with hexanes, and the flask can remain undisturbed while slowly cooling to allow for better crystal growth. It's worth waiting overnight.

If you really want to speed things up, a better choice for purification would be FASA fumarate precipitation.
 
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Mindlusion said:
dry ice baths aren't really optimal for recrystallization, since the temperature change is far too dramatic, or not easily controlled for slow crystallization. As a result, you get fine crystals or precipitate, or worse, an oil that falls out and solidifies. Even the escaping CO2 bubbles in the dry ice bath are enough to disturb the flask and interfere with crystal growth.

Naphtha is also not the best solvent for freeze precipitation, its better to use hexanes. the tryptamines are more soluble in naphtha at low temperatures, and as it contains high boiling/low melting hydrocarbons, so it's not suitable for temperatures as low as -78C.

In this case, -20C with hexanes is plenty cold to induce complete crystallization, and in the freezer with hexanes, and the flask can remain undisturbed while slowly cooling to allow for better crystal growth. It's worth waiting overnight.

If you really want to speed things up, a better choice for purification would be FASA fumarate precipitation.
Click to expand...
Appreciate all the tips! Any advice for when it does precipitate as fine crystals? Exactly what happened, and I am unsure of how I could decant the naptha off while leaving the DMT behind. Would leaving it in the freezer longer be useful?
 
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I think I may have over reduced my solution, as it was precipitating out at room temperature. Could this be causing the DMT to precipitate into fine crystals? Would adding more solvent help to slow the process of precipitation causing larger crystals to form?
 
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Time is the primary factor, concentration comes a close second in this case.

(Much) slower cooling from a rather more dilute solution would yield larger crystals.

The clouding that occurred at room temperature left lots of mini-crystals which served as nucleation points when the temperature was dropped abruptly. At least it meant you didn't end up with a load of goo (although that's no tragedy, really).

Look into Ostwald ripening - that is a technique for turning lots of little crystals into fewer, larger crystals.

Another option is just to add a dash more naphtha, warm the whole thing up again until all the crystals have redissolved, then cool the solution down
s-l-o-w-l-y...
first to room temperature, then in the fridge, then (with insulation to slow the cooling) in the freezer.

Why the hurry, anyhow?
 
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