The Vespiary

The Hive => Methods Discourse => Topic started by: cheeseboy on February 10, 2002, 03:23:00 PM

Title: Choosing Non-Polars
Post by: cheeseboy on February 10, 2002, 03:23:00 PM
Cheese was told that DCM is far better than toluene to use as an extracting solvent for isosafrole epoxide from Oxone runs. Why is DCM better than toluene?  How about using distilled toluene, to get that H2O out in an azeotrope of toluene/H2O by distillation for 15 minutes?
May The Source Bee With You....Always.

Title: Re: Choosing Non-Polars
Post by: Flip on February 11, 2002, 02:41:00 AM
Boiling point of toulene is 110.63C, bp of DCM is 39.8C. I dunno dude you do the math.
Title: Re: Choosing Non-Polars
Post by: morpheus on February 11, 2002, 03:51:00 AM
Besides low bp,also non-flameable,and sinks to bottom.
Btw Rhodium said its one of his favorites.That alone
might bee enuff.
Title: Re: Choosing Non-Polars
Post by: Rhodium on February 11, 2002, 09:13:00 AM
There is no other non-polar solvent that I know which so effectively pulls EVERYTHING non-polar out of an aqueous solution. Therefore, there are some instances when ether is more preferable, when the aqueous solution is very very dirty, such as anything involving phenols/quinones. If ether is used, less of the gunk is extracted, and the extract is more easily purified afterwards, than if you had used DCM - as the DCM would have extracted much more of the unwanted gakk too.

I would never use anything else than DCM or ether if I didn't have to for extractions. Toluene for example has such a high boiling point, and petroleum ether is so non-polar that many desired things have a hard time dissolving in it, making many large extractions necessary to pull out what you want from the aqueous layer.
Title: Re: Choosing Non-Polars
Post by: PrimoPyro on February 11, 2002, 03:45:00 PM
Are all ethers created equally with concern to these properties? For example, the contrast between diethyl ether, THF, Dioxane, and dimethyl ether.

Would they all be interchangeable similar to how alcohols are exchangeable for one another?

Diethyl ether is something I'd rather not purchase, as it is List II here, but THF or Dioxane, don't seem to have any stigma.

And as a last quickie question, that is very very important: Is dry dioxane ether suitable for the Grignard Reaction? Would there be any problems due to its use that you know of? Dioxane is very easy to make. I will not buy diethyl ether, and THF is kind of expensive.

                                                     PrimoPyro
The Water Will Be Your Only Mirror
Title: Re: Choosing Non-Polars
Post by: Rhodium on February 11, 2002, 03:50:00 PM
THF is for example miscible with water, while diethyl ether isn't, so ethers are very different. But methyl tert-butyl ether is exchangeable for diethyl ether for most purposes, including Grignards and LAH reductions.
Title: Re: Choosing Non-Polars
Post by: cheeseboy on February 11, 2002, 07:31:00 PM
So why is it bad to use toluene for the iso-epoxide extraction. If a vacuum is used, then the temp could be 60*C . But doesn't the epoxide get heated even past toluene's BP in the thermal re-arrangement afterwards? What's up with that? Isn't the re-arrangement temp 260*C- 300*C?
May The Source Bee With You....Always.

Title: Re: Choosing Non-Polars
Post by: cheeseboy on February 21, 2002, 01:17:00 PM
WHAT'S WRONG WITH USING TOLUENE!!!!!!!!!! Why does the boiling point of toluene make a difference in this whole rxn, if a vacuum is used, then the boiling temp will bee even lower that 80*C. So is there a nasty problem using toluene to extract the epoxide?Wont the epoxide be OK while the toluene is boiled off under vacuum?
<-------Don't Bee Careless, Bee Carefull & May The Source Bee With You...Always..
Title: Re: Choosing Non-Polars
Post by: Chromic on February 21, 2002, 02:50:00 PM
Toluene will work. However, read what Rhodium said "There is no other non-polar solvent that I know which so effectively pulls EVERYTHING non-polar out of an aqueous solution.". DCM really is one of the best organic extraction solvents!

So to compare:

1) DCM is a better solvent than toleune
2) DCM is easier to recover than toluene
3) DCM smells better than toluene
4) DCM sinks to the bottom which is nice for extractions
Title: Re: Choosing Non-Polars
Post by: Vibrating_Lights on February 21, 2002, 05:56:00 PM
Toulene is only useful when there is solid garbage at the bottom that would require extra filtration.
Vl_
Title: Re: Choosing Non-Polars
Post by: slappy on February 22, 2002, 01:06:00 AM
PrimoPyro:

Are all ethers created equally with concern to these properties? For example, the contrast between diethyl ether, THF, Dioxane, and dimethyl ether.



Not quite. Dimethyl Ether is a gas, and therefore not used as a solvent. Diethyl Ether, THF, Diisopropyl Ether, and Methyl tert-Butyl Ether can pretty much be used interchangably. Dioxane is mainly used as a reaction solvent, and not for extractions due to it's high B.P. and carcinogenicy.

Diethyl ether is something I'd rather not purchase, as it is List II here, but THF or Dioxane, don't seem to have any stigma.

And as a last quickie question, that is very very important: Is dry dioxane ether suitable for the Grignard Reaction? Would there be any problems due to its use that you know of? Dioxane is very easy to make. I will not buy diethyl ether, and THF is kind of expensive.



Why not buy Ether? It doesn't have that much of a stigma. Et2O is used in large quantities in every lab that swim has worked in or seen. It is a VERY common and necessary solvent.

Yes, Dioxane is a very good solvent for Grignard reactions. However, it is a really powerful carcinogen. Ether is virtually non-toxic, you can spill it on yourself, breath it, hell, even drink it in small amounts (not recommended though). THF is a little more toxic, but still pretty innocuous. But heed my warnings about Dioxane, it is a very nasty carcinogen. Watch out.
Title: Re: Choosing Non-Polars
Post by: PrimoPyro on February 22, 2002, 11:37:00 PM
Thank you, Slappy. I am very safety oriented. I did not know about dioxane's toxicity. Thank you very much for the information!  :)

                                                    PrimoPyro
The Water Will Be Your Only Mirror
Title: Re: Choosing Non-Polars
Post by: cheeseboy on February 24, 2002, 04:37:00 PM
Ditto, cheese is OK now, cheese has all the info needed on extracting solvents. Cheers!! :)
cheesebot
         May The Source Bee With You...Always..