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Author Topic: Refluxing under inert gas  (Read 148 times)

gloves

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Refluxing under inert gas
« on: April 10, 2012, 09:36:23 AM »
Hello,

I was guessing if pumping N2 or Ar halfway inside a tall necked Erlenmeyer flask (stirring the solution with a magnetic stirrer) until all air is displaced (and then keeping the flow of inert gas active) would be sufficient to accomplish a reaction involving reflux in inert atmosphere.

Would using CO2-rich N2 work too or is CO2 being too reactive for most reactions?

 ;)
« Last Edit: April 10, 2012, 09:38:44 AM by gloves »

pyramid

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Re: Refluxing under inert gas
« Reply #1 on: April 10, 2012, 02:04:19 PM »
What is your substrate?

Also, what is your setup, you can't reflux in an erlenmeyer.

It is better to use argon in basically all circumstances, and degas the solvent by pulling a vacuum until ebullition and refill with Ar (do it 3 times). Otherwise, bubble gas through the liquid for several minutes.
If you don't have special adapters/flasks, get the tubing down through the condenser to purge the inside of the setup then attach a balloon on top filled with gas, or put some cotton wool on top to restrict air flow.

Usually you don't need a constant flow, especially with Ar since it sits over your reaction mixture. A degas and purge should work fine for most things, but I don't know your particular purpose.

jon

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Re: Refluxing under inert gas
« Reply #2 on: April 22, 2012, 04:52:37 AM »
especially gringnards and alkyllithiums have to have dry pure argon or nitrogen  because most welder's gasses contain co2 this is a pitfall for many.

POSEIDON

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Re: Refluxing under inert gas
« Reply #3 on: April 22, 2012, 05:20:11 PM »
Look this pdf, part of the VOGEL textbook
The chemists are a strange class of mortals, impelled by an almost insane impulse to seek their pleasures amid smoke and vapour, soot and flame, poisons and poverty; yet among all these evils I seem to live so sweetly that may I die if I were to change places with the Persian king.
— Johann Joachim

fresh1

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Re: Refluxing under inert gas
« Reply #4 on: April 23, 2012, 08:45:43 AM »
you really need to be able to purge the flask a couple of times to ensure all the air has been flushed which would work with a vacuum style flask with a side arm like you'd use with a buchner funnel
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gloves

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Re: Refluxing under inert gas
« Reply #5 on: April 23, 2012, 07:36:38 PM »
Many thanks!  ;D

Electro´S

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Re: Refluxing under inert gas
« Reply #6 on: May 11, 2012, 09:52:14 AM »
would be any possibility to remove the CO2 washing it through any solvent or reagent in a wash bottle (or a couple of its) from small tanks Ar/CO2 for wleding?.
« Last Edit: May 11, 2012, 09:57:30 AM by Electro´S »

embezzler

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Re: Refluxing under inert gas
« Reply #7 on: May 11, 2012, 12:39:08 PM »
Quote from: Electro´S on May 11, 2012, 09:52:14 AM
would be any possibility to remove the CO2 washing it through any solvent or reagent in a wash bottle (or a couple of its) from small tanks Ar/CO2 for wleding?.


There are easier ways to an inert atmosphere than this. Gasses are usually distilled to separate them. This requires more skill and equipment than is likely to be available

One would have to reduce the pressure to scrub the CO2 ( carboxylic acic anhydride ;) ) which would be a painfuly slow process high in uncertainty. 

Microbiologists generate anaerobic atmospheres for oxygen sensitive organisms. This is one example of generating gasses. There are others.

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