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Rotary evaporator not effective for chlorobenzene !
Posted: Tue Apr 19, 2016 12:51 pm
by thohry
Hi all,
We just started the aromatic amine analysis. In the SOP, we have to evaporate 25ml chlorobenzene by rotary evaporator at temperature < 60 oC. But at this temperature, I can not make the chlorobenzene evaporate, not a single drop !
The vacuum is about -0.8 bar (maximum), the rpm is also near the max. I can only set the temperature at 60 oC
Did I do something wrong ?
Thanks for any input.
Re: Rotary evaporator not effective for chlorobenzene !
Posted: Tue Apr 19, 2016 2:16 pm
by Don Shelly
You need to increase the vacuum pressure until you reach the boiling point of chlorobenzene at 60 C.
Re: Rotary evaporator not effective for chlorobenzene !
Posted: Tue Apr 19, 2016 4:19 pm
by Steve Reimer
With a normal boiling point of 131 degrees and your bath temp of 60 degrees it will take a good vacuum.
Back when dinosaurs roamed the earth I had a prep where I had to strip 1/2 liter of diaminopropane from a reaction mixture using a rotary evaporator. I could get the bath temp up to ~85 degrees. It took overnight, and that was hooked to a nice vacuum pump.
Re: Rotary evaporator not effective for chlorobenzene !
Posted: Tue Apr 19, 2016 4:30 pm
by Don Shelly
BUCHI has pumps that can accomplish this.
Re: Rotary evaporator not effective for chlorobenzene !
Posted: Wed Apr 20, 2016 3:37 pm
by thohry
Thanks all for responding.
Yes, it's the vacuum pump which isn't vacuum enough !
I haven't got a better pump in hand but another one of the same quality, so I install the two pump in series, and it works !
At least for the time the new vacuum pump arrives, I can use the dual vacuum pump system.
Thanks again.
Re: Rotary evaporator not effective for chlorobenzene !
Posted: Wed Apr 20, 2016 5:22 pm
by GOM
Steve Reimer wrote
Back when dinosaurs roamed the earth
That made me smile.
Regards
Ralph