Purity of a compound after crystallization

[Bandil]

Hi!

I decided to move the question here, as it was originally posted in general discourse, but i believe it is more apropriate here.

The original question is regarding DOB crystallization, but it is actually more generally speaking i am interested in...

"When the DOB was made after the bromination, the crystals where crashed in IPA/acetone and gave very clear prism-like crystals(totally white). Can one not assume that it is rather pure DOB if it forms crystals so readily and pretty?"

That was the original question, but i am still pondering how "similar" compounds can be, before they can crystallize together. For example if a mixture of DMA/DOB HCl is crystallized. Is it possible to make a poly-crystal which consists of both DMA and DOB or will only one of the two things form? Where does the line go, when speaking of crystallizing? Can one for instance crash/grow crystals of all the different PEA's in one big batch or what are the limitations?

Regards
Bandil

[Megatherium]

If a mixture of DMA/DOB HCl is crystallized. Is it possible to make a poly-crystal which consists of both DMA and DOB or will only one of the two things form?

When the DOB was made after the bromination, the crystals where crashed in IPA/acetone and gave very clear prism-like crystals(totally white).

Well, all depends on how you crash-crystallized the DOB.  What you 're doing with the IPA/acetone mixture is called "cold crystallization".  One normally puts the crude product in solvent A in which it dissolves, and then one adds dropwise another solvent B (in which the DOB isn't soluble) until tiny crystalls are appearing.  Then you wait a few hours and later, the erlenmeyer is placed in the fridge, to complete crystallization.  Crystallization takes time!  The more gradually a product crystallizes, the more pure it is.  One can eventually add some more solvent B, but the prefered procedure is: filter off the crystalls & repeat the procedure all over again with the residue.

If you mean by crash-crystallization: I dump the crude product in a IPA/Acetone mixture and the "crystalls" precipitate directly, then there is a fairly high possiblilty that the DMA gets trapped in the crystal-matrix & you get co-crystallization with as result an impure product   .

Try dissolving the DOB in eighter IPA or acetone (don't know in which it dissolves) & then add gradually the other solvent.

[Rhodium]

That was the original question, but i am still pondering how "similar" compounds can be, before they can crystallize together.

They need not be similar at all.

For example if a mixture of DMA/DOB HCl is crystallized. Is it possible to make a poly-crystal which consists of both DMA and DOB or will only one of the two things form?

A mix can be obtained, but need not to. The likelyhood of impure crystals (a mixture) forming is proportional to the amounts of the stuff you have in solution to begin with. If you start out with a 1:1 mixture of each, then a mixture is VERY likely to result from crystallization, but if it is a 1:100 ratio, then the resulting crystals are very likely going to be pure (when crystallizing slowly and not crashing out everything). But you can never know for sure until you have tried it.

Where does the line go, when speaking of crystallizing? Can one for instance crash/grow crystals of all the different PEA's in one big batch or what are the limitations?

There is no set line, it is just more difficult to crystallize something pure if you have many contaminants and/or contaminants present in large amounts. But if you repeat a recrystallization over and over, your sample will become purer and purer (in most cases), but you will at the same time experience loss of some for each operation.

[Lilienthal]

If you are talking about co-crystallizates where both compounds are in the same crystall structure: That's very, very uncommon (non-existing for your purposes   ). From time to time you get solvent or water incorporated into the lattice.

[fierceness]

If you are talking about co-crystallizates where both compounds are in the same crystall structure: That's very, very uncommon (non-existing for your purposes ). From time to time you get solvent or water incorporated into the lattice.

If that is true, how is it that so much methamphetamine sold "on the street" is a mixture of MSM and methamphetamine within the same crystalline structure?  You can purchase shards of street-grade meth that looks like 4-5mm shards of glass but it most definitely has both MSM and Methamphetamine in there.

[foxy2]

The MSM is probably acting like a solvent.  I doubt those shards are crystals but more like an amorphous ice cube with meth dissolved in it.

[fierceness]

The MSM is probably acting like a solvent.  I doubt those shards are crystals but more like an amorphous ice cube with meth dissolved in it.

That makes a lot of sense.. when attempting to vaporize meth sold in the street (supposedly "good shit", big pretty crystals) the crystals turn to a considerable amount of what looks like water, but is probably MSM.. when vaporizing better-than-street-grade meth, only a small amount of liquification is noticed.