[Vermilion]

Theoretically is it possible to crystallize any organic compound? What are the limitations to crystallizing compounds and what are some of the contributing factors that make it easier for some compounds versus others? (easier to crystallize that is)

Really curious about this one!

[PhDoc]

This sounds like a question given by a professor of a lab section as a thought exercise.

[orgopete]

If melting occurs when (weak) bonds are broken, then a higher melting compound would have bonds? This isn't covalent or ionic bonds being broken. When ice melts, what bonds are broken?

[zsinger]

Exactly as Lennox said, this is a SUPERB test question, and actually one I got asked in my undergraduate lab section about 5 years ago.  Requires thought and not necessarily too much knowledge.  Orgopete has set you on the correct path.  Think about the physical process  of "melting" or "crystallizing".  Wikipedia them both, and see exactly what they mean.  I think you will grasp this question much more firmly.

[Vermilion]

It seems dependent on the solubility of the compound in its solvent, its degree of supersaturation and the compound's intermolecular forces. Thanks for the insight!

[java]

..however crystallization is often mistaken for dissolving a material in a solvent the evaporating off the solvent to a solid material.....that is not crystallization, one needs to use a solvent that the material is not soluble in at RT, but soluble hot, then by using minimal amount of this hot solvent to dissolve the compound , then allowing it to cool in the freezer or in a coolarea without movement....then the solvent can be removed to get pure crystallized material.....well almost,one can repeat this several times to get purer material.....java

[discodermolide]

Dear Java,
Movement during crystallisation can be very important, for example, to obtain the correct particle size, the correct modification, to stop clumping of crystals, get the correct bulk density. I would always advocate movement, even to get crystals of x-ray quality.

[java]

...that may be true , as to movement, but found that leving the material alone at least overnight one can get very large tranlucent crystals , where with movement the size is never aquired....java

[discodermolide]

...that may be true , as to movement, but found that leving the material alone at least overnight one can get very large tranlucent crystals , where with movement the size is never aquired....java

Size is not everything.

[zsinger]

Size is not everything.

Disco……I am quite confused by this concept you have described of "correct bulk density".  Could you elaborate?  Thanks!
            -Zack

[discodermolide]

Bulk density refers to the flowing properties of a solid, essentially how easy it it to be placed in a machine for filling into bottles and pills.
perhaps this will give you a better idea http://en.wikipedia.org/wiki/Bulk_density.
Large crystals will not flow so freely as small crystals. They will also not pack together as well as small crystals. This can be compensated for by milling the compound to a defined particle size. But this can also be controlled by the crystallisation conditions. This is important as the particle size of a pharmaceutical is defined within tight limits as is the bulk density. These things can affect the solubility of a drug and hence its re-sorption into the body and hence its efficacy.
So tight control of these things starts with the crystallisation.

[zsinger]

Makes perfect sense!  Thanks as always!
        -Z