[Messi]

Hi,

I have a 8:1 Hexane:EtOAc. How long would it take me to rotoevap it?

[synthon]

Hexanes comes off fast and without bubbling; nothing's smoother than hexanes.  EtOAc takes longer, and will need to dry under high-vacuum to remove completely.  At 40C and typical vacuum, prob ~10-20 mL/min.

[Messi]

Hexanes comes off fast and without bubbling; nothing's smoother than hexanes.  EtOAc takes longer, and will need to dry under high-vacuum to remove completely.  At 40C and typical vacuum, prob ~10-20 mL/min.

Ok nice. I did my rotoevap but my none of my solvent evaporated off. I had about 2-3mL of it. I let it rotoevap for 30min. but nothing happened.

[synthon]

I'd bet that 2-3mL is your product, or you forgot to close the vacuum.

[Messi]

I'd bet that 2-3mL is your product, or you forgot to close the vacuum.

I probably forgot to close the vacuum

How do I do that if the picture below is my rotoevap?

[Messi]

I guess my question is: how do I close pressure valve rotary evap?

[synthon]

The nozzle at the very top left of the picture should rotate.  With the vacuum switched on and the valve open, you'll hear air whizzing through it.  Just rotate it closed, until there's no air.  Also make sure that the condenser is running, so that you can collect the solvent you evaporate, instead of sending it into the vacuum.

Sounds like you might need to find someone nearby to give you a crash course?

[Messi]

Sounds like you might need to find someone nearby to give you a crash course?

Yes, good idea I just read somewhere "To close the vacuum valve, turn it so that the knob is perpendicular to the bench, pointing toward you."

By the way, is this site reliable if I want to know Rotovap conditions?

http://www.chem.rochester.edu/safety/rotovap_cond.php

[Borek]

Crash course - in the context of working with a vacuum - doesn't sound good 

[synthon]

perpendicular to the bench, pointing toward you

Seems contradictory, no?  Should read 'parallel to the bench(top)'. 

The website hosted at rochester is great for all kinds of tips for all levels. NotVoodoo is the main page, I probably spent a full day there in my early days.  There's probably a good list of helpful websites documented here somewhere...anyone got a link?

[Messi]

perpendicular to the bench, pointing toward you

Seems contradictory, no?  Should read 'parallel to the bench(top)'. 

The website hosted at rochester is great for all kinds of tips for all levels. NotVoodoo is the main page, I probably spent a full day there in my early days.  There's probably a good list of helpful websites documented here somewhere...anyone got a link?

The rookie mistakes section there is hilarious and very helpful. A nice combination!