[voidSetup]

Is there any way to try and predict if a product/intermediate will be a solid or liquid/oil at room temperature after a reaction?  I know that if you can form an ionic bond then the material might be able to be crystallized.  If that is not the case though, is there any way to predict it based on the molecular weight of the material or its functional groups?

[Honclbrif]

There are apps which will predict mp/bp from structure, but their results should be taken with several grams of salt. A decent place to start is http://archemcalc.com/sparc/.

Otherwise, predicting general trends in mp generally goes back to freshman chem: species which are primarily aromatic, species with a large dipole moment, and ionic species all tend to be solid at RT. The weird exception is some species with nitrogen cations can have weirdly low mps (see ionic liquids).

[voidSetup]

hmm, ok that makes sense.  Assuming then that you're product is a solid, during the workup should you not use a drying agent like MgSO₄ since you're product will precipitate out anyway?  Will the drying agent get stuck in the crystals of your product?

[Honclbrif]

Usually when you dry your product it is dissolved in organic solvent. You can just wash the MgSO₄ with the same solvent a few times to make sure you've maximized your recovery. Then vap off the solvent to recover your product.

[voidSetup]

Ok cool.  I ran a reaction last week and when I got the the drying stage, I added the MgSO₄ and it kind of stuck to the bottom of the erlenmeyer all over the place.  Usually it clumps together, so this was unusual.  When I rotovapped the solvent off I was left with a few white crystals in an oil.  The oil is some left over starting material and some side products that I'm aware of, but I think the white crystals that were left are my product.  It's not ionic but has a molecular weight of about 500 (29 carbons and some other stuff) so I figure it could maybe crystallize at room temperature.

Thanks for the tips!