I can't be the first person to do something like this. This is how I did the last two reactions of my PhD after RMIT declined to provide me with a Schlenk line. Using unloved glassware and rubber tubes, I cut things to size and clamped them in place to fit together a single tap system to toggle between vacuum and nitrogen. The nitrogen comes from the blue tap and passes through CaCl2 before entering the 'system'. Excess nitrogen exits through the bubbler at the bottom by passing through silicone oil that prevents the entry of moist air. I had the bubbler at the top at first, but the oil was too easily sucked into the system so I moved it to the bottom. House vacuum comes from the grey tap and the vacuum and nitrogen are both available to the splitting tap on the right which is labelled and easy to reach. As I was doing this reaction in 1,2-DCE at 70 °C, I chose to use an air condenser which is easier to flame dry than a water condenser.
In case you are wondering, the red taps are for steam, the green tap is water and the blue tap is air. The internal width of this fumehood is 93 cm.
In case you are wondering, the red taps are for steam, the green tap is water and the blue tap is air. The internal width of this fumehood is 93 cm.
Here I have used the setup again, this time for a reaction in DMF at 140 °C. I allowed a slight positive pressure of N2 to bubble slowly through the system which is an exit point for any unexpected pressure. When used in this way the air condenser worked perfectly well to contain the DMF; the top was cool even when the bottom was at 140 °C. I placed the fan there merely as a precaution.
A retired Professor friend of mine reminds me that more effective anhydrous conditions can be achieved when the nitrogen/vacuum delivery inlet is instead placed at the top of the condenser. I will remember this for next time.
He also shares with me a design for the bubbler which makes it harder or near impossible to suck air back into the system. It is made up of two Dreschel bottles (like the one containing the CaCl2 in the above image) which are placed in series, with the first reversed. The second is almost filled with oil, which the nitrogen bubbles through. Any suck-back results in the oil in the second bottle sucking into the first, and only after almost the whole volume of oil has been transferred can air get in. Turning up the nitrogen transfers the oil back to the second bottle.
A retired Professor friend of mine reminds me that more effective anhydrous conditions can be achieved when the nitrogen/vacuum delivery inlet is instead placed at the top of the condenser. I will remember this for next time.
He also shares with me a design for the bubbler which makes it harder or near impossible to suck air back into the system. It is made up of two Dreschel bottles (like the one containing the CaCl2 in the above image) which are placed in series, with the first reversed. The second is almost filled with oil, which the nitrogen bubbles through. Any suck-back results in the oil in the second bottle sucking into the first, and only after almost the whole volume of oil has been transferred can air get in. Turning up the nitrogen transfers the oil back to the second bottle.
