[lukeasaur]

Hi internet,

I am trying to run a reaction, and subsequently distill it, but it needs to be large scale (4L reaction flask) in order to get a decent yield. The particular reaction is making DMDO from oxone and acetone, which gives about 5% yield and ~0.5-0.9M DMDO in acetone. The org. syn. prep calls for a mechanical stirrer, and my colleague, who has done this before, claims that a giant stir bar just won't cut it. Is there a feasible way to do this without a mechanical stirrer? We do not have one in any of the labs in the department.

Thanks!

[organicadam94]

IMHO If everything's in solution, then there is no overwhelming need to stir the flask in the first place.  Assuming you're heating the mixture, then the thermal energy will keep the molecules moving enough to ensure that everything is evenly distributed throughout the flask.  And obviously, with distillation, one never really uses a stirrer bar.

Just my opinion, I know many people wouldn't think of running a reaction without stirring, but I've never noticed any problems when I've been running simple reactions.   

That said, I don't often run 4 L reactions....

[discodermolide]

Sorry organicadan94, this is just not true. Stirring is vital, especially on scale. It promotes vital heat transfer throughout the medium, without which you may end up with an adiabatic runaway decomposition. Especially in this case.
As to the OP, a mechanical stirrer is obviously the best option, if you can borrow one do so, there must be one somewhere.
Why distill the DMDO anyway, I'm not sure it is thermally stable at the acetone BPt. I would check that out before you do it, as a 4L scale is large for a lab scale prep.

[408]

Find a power drill, stick a shaft with a stirring implement on the end in the drill.  If metal wrap the stirring implement with teflon tape.  clamp drill to stand.  You now have a mechanical stirrer. Used to do this all the time.

[discodermolide]

Find a power drill, stick a shaft with a stirring implement on the end in the drill.  If metal wrap the stirring implement with teflon tape.  clamp drill to stand.  You now have a mechanical stirrer. Used to do this all the time.

These are not explosions hazards? Or was it a special drill?

[408]

Just a regular drill.  We did it in partly sealed 3L RBFs (2 necks stoppered, one open for stir rod) and relied on a strong fumehood flow rate to keep solvent conc. in air low.  If you can run a bunsen in your hood, you can do this.  Industrial scale would be a whole other issue.

[curiouscat]

Find a power drill, stick a shaft with a stirring implement on the end in the drill.  If metal wrap the stirring implement with teflon tape.  clamp drill to stand.  You now have a mechanical stirrer. Used to do this all the time.

These are not explosions hazards? Or was it a special drill?

Explosion hazards are often not considered in academic labs, somehow. We had standard refrigerators and light fixtures in a lot of labs strangely.