organicchemist25 - 6-8-2018 at 18:48
I have a question on a recrystallization I just did. Ethylenediammonium Diacetate, to be exact. Im comfortable and fairly seasoned on recrysts. This
recrystallized with beautiful, long needles, but was above the surface of my solvent, MeOH. Is it ok for crystals to be out of solvent after removing
from the fridge or freezer, or should I typically use a little more solvent during the work up to keep the crystals under solvent?
I know the key is to use least amount of solvent when hot to dissolve impure product.
Thanks
[Edited on 7-8-2018 by organicchemist25]
j_sum1 - 6-8-2018 at 20:10
Probably what you have happening here is crystal creep. Capillary action causes the solution to flow along the surface of the crystals and then
evaporate, thus growing the crystal. For some substances this can cause crystals to completely escape from the container they are in.
Theoretically these crystals growing outside of the solution could be of lower purity than the others. This is because the crystallisation mechanism
is evaporating to dryness and there is no solvent to carry impurities away. Practically, I think you will find there is little real difference in
purity. If you are worried you could always do a recrystallisation. That is likely to result in lower loss of yield than if you greatly increase the
amount of solvent.
organicchemist25 - 10-8-2018 at 17:47
Not sure if this will help but I’m attaching a picture of it. They came out very nice and clean. It’s just that the solvent was beneath top layer
surface of the crystals. Maybe this is what you are referencing to...
Appreciate your help
