Try to find out metastable zone and see how good it is.......sometime a slow addition of water in IPA gives crystalline .........I am wondering whether this compound is made anytime crystalline...........otherwise contact me @9916128470 for further discussion.

HI,

what's the nature of your substance? Maybe you could try recrystallization from other solvents...or add some little amount of solvent, in which your substance is insoluble. Or you might add some seed crystals (if availabe)..or you simply scratch with a glas bar on the beaker wall to induce crystallization...or you try freeze drying...

Kind regards,

Simon

If your compound`s nature is crystalline then you can get crystalline form by using solvent in which compound is insoluble, and heat it up to its melting point, after complete melting immediate filter and let it cool and crystallize.

Try to disslove in ether and let it crystallize it will come in crystalline form.

Maybe the compound is not pure enough? Try another chromatography and then recrystalize it if necessary.

This is the million dollar question.

Rather, the general answer to this question is worth millions of dollars - especially in the field of proteins

Please specify what kind of a compounds class is in deal

Hi, Rogoza its a hetero cyclic compound, having 5 nitrogen and two sulfur

groups

Hi Girish,

first question is about seed cristals - have you them or not?

Next questions -

1) is compoud dried ( in high vacuum) before crystalisation (from water and reaction\cromatographic solvents)

2) It was used DRY solvents for crystallization?

3) Compound is in SALT form (if basic)?

4) Can you CENTRIFUGATE ''gel like" crystals?

5) Is it not mix of stereoisomers?

My name is Andrei, Rogoza is family name )

Apologies Andrei, The answer for your question are as below.

* Even after long time vacuum drying in rota it is not in solid state (Purity is 91%) but after column I am getting good solid but amorphous form(confirmed by microscope study)

* LR solvent was used for crystallization, MC

Girish,

If you have a mixture of diastereomers, the purity is near 50% or less. If there is no seed crystal, it is difficult to hope for success. Although Pasteur was lucky - he was able to divide crystals with tweezers under a microscope. But in this case needed at first enrichment for individual diastereomers. Extraction from water layer with HALF of required optically active acid can help.

LR - means low rest? Water is main enemy!!!! And very "toxic" for crystallization EtOAc - it is often used as polar phase in the eluent. "Rota" is used usually with low-vacuum sources ( some mmHg), but in oil-pump vacuum many "oils" quickly become hard.

Centrifugation was pointed simply as alternative to filtration - in Amocons, Falcons or Eppendorf tubes

Dear Girish,

I would strongly agree with the previous comments and recommend that you first try to separate your diastereomers with the help of preparative HPLC. If after that you still face difficulties, you might have a look at our paper, a tutorial about single crystal growth:

https://www.researchgate.net/publication/230751079_Some_thoughts_about_the_single_crystal_growth_of_small_molecules

Good luck! Bernhard

Article Some thoughts about the single crystal growth of small molecules

Thanks Bernhard and Andrei for your suggestion.

Yes you are right, I separated the diastermers and tried to crystallize in IPA to get amorphous to crystalline and it was successful. This was further confirmed by XRPD pattern

Amorphous solid can be made crystalline only if we use opposite solvent for crystallization , by heating and filter quickly. After complete filtration allow for slow cooling as possible as. The compound formed will be kinetically crystalline but not thermodynamically.