Removing solvent without vacuum distilling

eyesoftruth · Fri Jun 24, 2005 6:51 pm

Hello. I am an extreme noob. I've been dabbling in Chemistry for a few months now and please go easy on me as I am young and inexperienced.

That said, I have a few questions.

So SWIM was successful in performing a synth. The thing is, at one point, THF and methanol have to be removed from the reaction vessel. SWIM uses vacuum distillation to remove it and it works perfectly. MY question is, can these be removed from the mixture without vacuum distillation? Noting that it wouldn't be prudent to heat the mix to a temp equal to or greater than 60 deg celcius.

Also, at another stage SWIM needs to remove CH2Cl2 and uses vacuum distillation. Maybe SWIM isn't doing it right, but very little of CH2Cl2 comes over. It most likely evaporates (I think). Not that SWIM needs to keep the CH2Cl2, but still it would be nice to collect it, purify it(if needed) and reuse it. What is SWIM doing wrong?

Finally, suppose SWIM didn't need to collect the Dyke, could SWIM just heat and stir the mixture to evaporate the CH2Cl2 from the required mix?

I hope I have been able to ask the questions correctly?

P.S. - Bandil, I've been following your work for a while. You are an inspiration.
Smile

EDIT: Sorry, corrected some terribly spelled words.

bio · Working Bee

It takes at least 30 deg or so temp difference to be able to condense in glass with any sort of reasonable efficiency. Forgetting the 60deg limitation for now, just adjust the vacuum to distill at a temp you are able to condense.

Using ice water cooling, dewar cold finger etc and chilled reciever brings it's own headaches, like keeping water out, from the air moisture condensing. With low boilers like Me2CO, ether, DCM, Pentane etc there isn't much choice if you want to recover it and not use dry ice in the condenser. Distill at atmospheric for these.

With toluene for example distill at say 60-70deg if you want to use vacuum just remember that separation is not so good without going slowly and using a short column at least.

Trying to evaporate from an open container will not remove all of the solvent unless perhaps in a very thin film which brings a risk of probably scorching the product along with numerous other problems.

Take a look at a vacuum pressure/temp conversion application and maybe this will help you. For example something boiling at 42deg atmos boils at minus 36 at 20 torr. Now how the hell will you condense it??

http://www.ch.cam.ac.uk/magnus/boil.html

eyesoftruth · Sun Jun 26, 2005 11:57 pm

Hey thanks bio, that's just the answer I was looking for.

You saved me a lot of second guessing.