Rotary evaporator not effective for chlorobenzene !

[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.

[Don Shelly]

You need to increase the vacuum pressure until you reach the boiling point of chlorobenzene at 60 C.

[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.

[Don Shelly]

BUCHI has pumps that can accomplish this.

[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.

[GOM]

Steve Reimer wrote

Back when dinosaurs roamed the earth

That made me smile.

Regards

Ralph