The Vespiary

The Hive => Chemistry Discourse => Topic started by: Elementary on June 18, 2002, 09:09:00 AM

Title: Drying Ether
Post by: Elementary on June 18, 2002, 09:09:00 AM
In most grignard procedures the ether to be used is normally refluxed with sodium to ensure that it is completely anhydrous.

My question is, can lithium metal be used to dry the ether instead of sodium ?

John Lennon - Working Class Hero
Title: Yes, that should work too.
Post by: Osmium on June 18, 2002, 09:27:00 AM
Yes, that should work too.

But the whole point becomes moot if you don't know how to properly handle the ether afterwards. If you simply put it into a bottle and have no idea about properly handling stuff under anhydrous conditions then such drying is pretty much useless.

I'm not fat just horizontally disproportionate.
Title: and if that is difficult
Post by: starlight on June 18, 2002, 12:38:00 PM
and if you are not able to maintain anydrous conditions, then maybe you could use ultrasound to initiate Grignard reactions....

https://www.thevespiary.org/rhodium/Rhodium/chemistry/grignard.wet.html (https://www.thevespiary.org/rhodium/Rhodium/chemistry/grignard.wet.html)



not that i have ever tried it.  :)

./
Title: Well, Os, you gonna keep those anhydrous ...
Post by: El_Zorro on June 18, 2002, 03:19:00 PM
Well, Os, you gonna keep those anhydrous condition tips to yourself, or are you gonna share 'em with the group? ;)

Do not go gentle into that good night.  Rage, Rage, against the dying of the light.  --Dylan Thomas
Title: Well, obviously you shouldn't pour that ether ...
Post by: Osmium on June 18, 2002, 03:31:00 PM
Well, obviously you shouldn't pour that ether from a flask into a bottle through a funnel! Store it in the flask under inert gas, transfer it with oven-dried pipettes, syringes or flexible, needle-tipped teflon hoses, always use dry N2 or Ar, dry all your glassware and everything else before use and purge them with the gas, find out what Schlenk glassware looks like etc.

http://www.ilpi.com/inorganic/glassware/vacline.html (http://www.ilpi.com/inorganic/glassware/vacline.html)


http://www.ilpi.com/inorganic/glassware/schlenkflask.html (http://www.ilpi.com/inorganic/glassware/schlenkflask.html)



I'm not fat just horizontally disproportionate.
Title: Dehumidifier
Post by: lugh on June 18, 2002, 04:55:00 PM
Those are all good tips, but bees should know that in addition to what was previously posted, SWIL likes to keep the humidity down with a dehumidifier; since SWIL doesn't live in the desert  ;D
Title: I wanna know why nobody uses CO 2 as an inert ...
Post by: El_Zorro on June 18, 2002, 07:57:00 PM
I wanna know why nobody uses CO2 as an inert gas.  It's gotta be the cheapest and easist gas to buy, and it is completely unwatched.  Not to say the other gases are watched, just that CO2 is less watched.  Is CO2 not inert enough?  Is it not dry enough?  Why does no one use CO2?

Do not go gentle into that good night.  Rage, Rage, against the dying of the light.  --Dylan Thomas
Title: Won't most Grignards react with C02?
Post by: Bwiti on June 18, 2002, 09:17:00 PM
Won't most Grignards react with C02?

Love my country, fear my government.
Title: CO2
Post by: former_chemist on June 19, 2002, 12:08:00 AM
CO2 is sold for use as an inert gas for welding.  Argon is prefered though. Nitrogen is also used but that depends on the metal, some form nitrides which is either good or bad depending on the application.

Oh you mean for a chemical reaction!  CO2 is fine as long as your reaction isn't harmed by acid. CO2 reacts with basic compounds and complexes (like sodium and magnesium) to form carbonates.
Title: Carboxylic Acids
Post by: lugh on June 19, 2002, 03:18:00 AM
Carbonation of the Grignard reagent is a standard method for preparing carboxylic acids, unless that's the product desired, one shouldn't introduce carbon dioxide  :)
Title: Dryness is relative.
Post by: terbium on June 19, 2002, 08:46:00 PM
Is it possible to dry ether with epsoms? 
Dry enough for use as the solvent in a Grignard reaction? Probably not, magnesium sulfate is not a very powerfull drying agent.
Title: I meant in relation to shit like keeping ether ...
Post by: El_Zorro on June 19, 2002, 09:31:00 PM
I meant in relation to shit like keeping ether anhydrous while you're getting it into a flask for storage, storing the ether under CO2 for storage, etc.  I would go ahead and use Ar anyway for a reaction.

Do not go gentle into that good night.  Rage, Rage, against the dying of the light.  --Dylan Thomas