[The Guy]

Hello fellows

yesterday I used MgSO4 to dry my crude. That was after a solvent extraction using NH4Cl/H2O and my organic layer was EtOAc.

After I added the drying agent to EtOAc it became solid and aggregate together, I added more and more, and the flask was getting warm and more warm. Until I got to the point that the whole flask is solid as a rock, and my product trapped inside that solid MgSO4.

This isn't the first time I experience that. I tried adding more solvent, but it wouldn't help, the Magnesium sulfate still solid.

Any suggstion? 

[discodermolide]

A silly question, but did you remove the NH₄Cl /water layer before adding the drying agent to the organic layer?
I ask because this usually happens when too much water is present.

[The Guy]

The aqueous layer was removed, but there was around 0.5 mL of water I didn't remove because I didn't want to lost my product. That what made confused, the moisture isn't that much.

[discodermolide]

Another silly question: was the mag. sulfate anhydrous?

[The Guy]

yes, otherwise it wouldn't react in that way.

The other time I experience it with THF and it was different rxn.

Thank you for helping discodermolide. Guys like you made this forum special.

[TheUnassuming]

This might not be important, but what solvent did you run the reaction in and how much water/EtoAc did you use for the extraction?  When I run reactions in THF and a few other solvents, there is definitely more water in the organic phase after extraction than with some other solvents. 
Maybe if the ratio of reaction solvent vs solvent in the extraction system is too high you can get sufficient levels of water in your "organic" phase to cause what you see.  It could also be helped by certain reagents in your reaction system.

[The Guy]

hmmm

My reaction solvent is DMSO, reaction was quenched by water 30mL then extracted using EtOAC, and I had difficulty have two layer separated.

[discodermolide]

If that's the case then you must have carried a lot of water over not the organic, because of the DMSO.
Try extracting with brine, perhaps the layer separation will be better.

[The Guy]

Indeed this was my problem. I tried the brine as u suggested but it didn't help. I got two layer, both of them has a significant amount of water and EtOAc.