[Gingie]

I have a question..

So i will be refluxing glycol under argon gas to simulate a closed system. I have a reflux column and a 3-necked ball flask. I am wondering if the following setup would work:

To purge the air:
Left neck of ball flask connected to argon gas, with regulator
Middle neck connected to stoppered reflux column
Right neck connected to vacuum, or just open

To begin refluxing:
Left neck of ball flask connected to argon gas, with regulator
Middle neck connected to open reflux column (to avoid refluxing under pressure)
Right neck stoppered.

Ive noted that bubblers are recommended on top of the reflux column; are these necessary in this setup? Also, argon is such a heavy gas, wouldn't any possible air entering be far away from the boiling glycol?

[DrCMS]

I would suggest connecting the argon to the top of the reflux condenser via a bubbler and leave it there.  To purge open one of the side ports on the flask and turn up the argon flow.  Once purged re-stopper the flask and then slow the argon flow down to just bubbling.  If you put the argon on to the flask itself you risk flushing the solvent vapour out of the top of the condenser without condensing it.

[wildfyr]

A little trick to force inert gas to flow through the reaction flask and not the bubbler is to open the flask (or insert a needle into a septum) and place your finger or a pipette bulb over the oil bubbler. With no outlet through the oil, the gas will pass through the flask and displace air. Do this for a couple minutes and you should be reasonably air free.

I don't know how air-free you need things to be, but unless you've done something like dry the solvent with sieves and sparged it with inert gas, there will be some water and oxygen in the solvent already even if you clear the headspace with argon.

And I agree with DrCMS, typically the gas source goes on top of the condenser. Otherwise you will be condensing solvent in the hose, not just the condenser. It will run back in to the reaction, except now its nice and contaminated.