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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Roentgenium on March 04, 2015, 01:07:39 PM

Title: acetone in plastic container at -80°C
Post by: Roentgenium on March 04, 2015, 01:07:39 PM

Dear fellow chemists,

In school im running a project to make a conductive polymer (PFO). The polymerisation is done with a cross-ccross-coupeling suzuki reaction. To make the monomer ready for polymerisation, a reaction with butyllithium is done at -80°C.
This temperature is reached by mixing dry ice with acetone. The thing is that we only have a plastic container that has been converted into a dry ice temperature bath for the reaction. A round bottom flask is used for the reaction and this flask dips into the acetone.
At room temperature this bath degrades due to the acetone on plastic.
My Question to you is if the degrading of the plastic stops below a certain temperature? At -80°C the plastic should become harder and maby solubility becomes lower to?

Any experience or knowledge about plastic degration in acetone is more than Welcome!!

Thanks for your time,

Jeroen

Title: Re: acetone in plastic container at -80°C
Post by: Arkcon on March 04, 2015, 02:33:00 PM

Numerous on-line sources reference what plastic resists what solvent.  I'm sure you can find one, if you wanted to change your vessel.  But you seem to imply that you can't change the vessel.  Otherwise, I would just use a glass dish inside your cooling bath.

Title: Re: acetone in plastic container at -80°C
Post by: Enthalpy on March 04, 2015, 03:54:30 PM

Is your operation with butyllithium too safe and easy, that you insist conducting it with the wrong hardware?

Search for
"compatibility list" acetone <name of a polymer>
to know which one to use. Very banal materials and items resist acetone.

Title: Re: acetone in plastic container at -80°C
Post by: orgopete on March 05, 2015, 08:00:28 AM

I am only guessing from the description, but this sounds like déjà vue. I remember chemists using a polyurethane(?) foam ice bucket for a low temp bath. These will swell up if used with acetone at low temp over time. This was before large Dewar baths were available. You could add a glass dish inside to hold the acetone-Dry Ice or what some of us did was to buy a cheap plastic insulated container that had a polyethylene liner in a polyurethane insulator. We cut them to size with a hacksaw and used these as Gonzo Dry Ice baths.