This is not actually true. Slow-growing long, contiguous, crystals is a purification process, not just something done for aesthetic purposes. As the crystal forms, impurities are pushed to the outside of the lattice formation, mostly locked out. This is where a two-solvent recrystallization comes in and is important. The second solvent scrubs clean each new layer of freshly formed crystal lattice as it's forming. Once formed, the impurities trapped in the second solvent can be removed through filtration. Purity is thus improved. The slower the recrystallization, the larger and more contiguous the crystals will be, as you know; but this also means purer crystals.
True. I recall reading (I think this was in something Strike wrote, perhaps Total Synthesis II, can't remember) something about the common impurities of MDA and MDMA being isolated and tested and how they seemed to have a counteracting effect to CNS stimulation. This is interesting.
I think so, but I've also had some incredible trips on what was described as dirty acid by others… I had this Lavender in liquid form circa 2000-2001 that was some breathtaking stuff.
Aztec – so good.
the idea of purification with crystalization is not to make big crystals.
we use a dual solvent and nearly crash the crystals out to get our first recrystalization.
we then do it again.
each time as the crystals are so small the solvent keeps the impurity.
once we have it at the purity we want (still white fluff) we then use a single solvent to grow the crystal.
if one puts an impure substance in a single solvent and then slowly crystalizes it there can be three possiblities that I can think of.
1 as you say the crystal matrix forces out impurity (normally works for impurities that are drastically different from chemical you are trying to purify)
2 you dilute the impurity and then crystalize it into the crystal diluted.
3 you can often crystalize solvent in some cases into your chemical depending on solvent and chemical being used.
best bet is after HPLC do three dual solvent crystalizations for purity then if you want to make it look nice one single solvent crystalization to grow the crystals from.
its the same for all crystals mostly, ICE or meth being the most common that we use here and after a resolution from DL meth this process is exactly what should be followed as well.
so big crystals can be seen as a sign of purity but then again they can also not be.
it all depends on if the impurities will fit nicely into the crystal matrix with out upsetting the way they stack.
something of note for acid (though I can not be 100% sure but it makes sence) we are dealing with amides that are all very simular in shape and polarity (does not vary anywere near as much as amines and acids do)
I would guess that a lot of ergolides will stack quite happily in the crystal matrix because of this.
so say we do a curtius on LSA to get to LSD.
the LSA and any broken amide could quite possible crystalize into the matrix if not purified correctly.
think of the crystals made by mixing things like meth and isopropyl benzyl amine.
or the fact that meth and amphet do not stack when racemate yet all of the other phenethylamines do.
there structure is more complex so there is more gaps in the matrix for impurity and optical isomers to co crystalize.
now think LSD is one big and complex molecule its bound to have heaps of things that will fit in the gaps between the molecules in the matrix.
I have never been able to form a large meth crystal from resolution of DL unless I do multiple dual solvent recrystalizations first and then go the single solvent.
that is because meth is so tight and simple in its structure so it wont let most impurities crystalize with it.
this its self proves that growing crystals in a single solvent is not the way to make pure substances though it does argue in your favour of big crystals means pure until we take the rest of the phenethylamines into mind
and the complexity of acid as a molecule.
then we can look at tryptamines like DMT.
how many get large yellow crystals of DMT.
DMT is clear.
"Crystallization is frequently used to affect a separation. The ability to achieve purification of materials that are free of impurities at the parts per million level is due to the ordered lattice of a crystal, and more precisely, the energetic penalties for disrupting this order. In order for an impurity to enter the lattice substitutionally (Figure 3.10), impurity molecules must replace host molecules at lattice sites. If the two species are significantly different in size, shape, or chemical composition, this replacement can only be achieved at the expense of distorting the crystal lattice. Distortions, in general, cost a great deal of energy, and thus are energetically unfavorable, i.e., the total energy of the soUd solution is greater than the energy of the two pure solids, each in an undistorted crystalline state (Sandler 1977)."
and
"impurity uptake is proportional to the concentration of impurities in the crystallizer, xuig, thus efforts should be made to minimize their formation or introduction into the crystalhzation stage; and (2) the segregation is predicted to improve with increasing solute concentration, XH.iiq"
from
so if the molecules are alike as many impurities in synthesis can be they will fit into the matrix with out kinking it and distortion.
so large crystals are not a way to purify and as stated in my bad copypasta above (blame the ocr of sciencedirect) it is best to make sure there is efforts made to minimise there concentration in the final crystallisation
which is done either by chromatography dual solvent crystallisation or a myriad of other purification techniques.
