ChemicalSolution (Hive Bee)
03-25-02 11:16
No 287592
      help- ether synthesis  Bookmark   

Julia know's all about the H2SO4/EtOH diethyl ether synthesis...

Lets say SWIM wanted to make benzyl ethyl ether from benzyl alcohol and etBr.  Any procedures out there for these higher MW ethers??? 

What about this KOH/DMSO ether synthesis that SWIM has heard of?  Is there a detailed procedure out there for this?/

Also--  are there ethers that Victor Grignard would NOT approve of???

xoxo Julia
 
 
 
 
    Rhodium
(Chief Bee)
03-26-02 11:36
No 288057
      Williamson ether synthesis  Bookmark   

When making ethers with an alcohol and an alkyl halide, the alcohol must usually be deprotonated for the reaction to proceed smoothly - that is, a base is added. Compare with the classic methylation of phenol, where PhOH + KOH + MeI -> PhOMe + KI + H2O, first the base reacts with phenol, forming water and potassium phenolate (PhOH + KOH -> PhOK + H2O). Potassium phenolate is much more reactive towards methyl iodide than phenol itself, and tus the reaction goes fast and smooth (PhOK + MeI -> PhOMe + KI).

If you are using an aliphatic alcohol instead of a phenol, KOH is usually not basic enough to completely convert the alcohol to the alkoxide (alcoholate) and a stronger base must be used, such as NaH, which irreversibly forms the alkoxide (ROH + NaH -> RONa + H2).

There are ways around the use of a stronger base, which either involves the use of a polar aprotic solvent (like your DMSO above) or alternatively the use of a PTC like TBAB/Aliquat 336 or other. The latter is much preferable, due to environmental, economic and practical viewpoints. If the reaction is performed with microwave heating, a solvent is not even necessary.

An example which combines the above advantages can be found at http://www.cyf-kr.edu.pl/~pcbogdal/alcohol/

If you don't want to do it in a microwave, check out the references at the above page.
 
 
 
 
    ChemicalSolution
(Hive Bee)
03-27-02 01:55
No 288300
      thanks, Rh!  Bookmark   

There's a procedure for ethyl butyl ether in a microscale level that starts by refluxing some NaOH in etOH.  Then the halo-butane is added and refluxed some more.  From memory, it seems that a 2x molar ratio of halo-butane to etOH was used.

Hmmmm... Julia wonders if much butyl alcohol was made in the process...

Soo.. Lets say SWIM wanted to make benzyl ethyl ether.. First, would this bee OK for the Grignard?  Second, if she has benzyl alcohol, which would be the best route?  Trying to make NaO-CH2-Ph by refluxing in NaOH or making X-CH2-Ph and adding it to a Na-O-CH2CH3 (or Na-methoxide)?------ cuz, SWIM called the big orange store (she really didn't) and they are fresh-out of sodium hydride.

If worst comes to worst, she'll try that DMSO method (you don't have a write-up, by chance, do you?).. The only problem is that DMSO is such a pain in the arse to rid your product of... Especially if SWIM's ether boils around 150C.

xoxo
Julia
 
 
 
 
    Rhodium
(Chief Bee)
03-27-02 02:32
No 288311
      Grignard ethers  Bookmark   

I have never heard of such a bulky ether as benzyl methyl ether being used for grignards, if I would just guess, benzyl methyl ether would not be a good grignard solvent. I believe there is a document on my page discussing alternative grignard solvents.
 
 
 
 
    ChemicalSolution
(Hive Bee)
03-27-02 04:46
No 288385
      Help Rh!!  Bookmark   

Ok-- What SWIM desires is an ether to use for a Grignard rxn that won't attract unwelcome attention.

THF is one option.. However, SWIM ain't scared to make her own ether....

Are et2O and THF used b/c of their (somewhat) higher polarity??  Maybe this helps facilitate the formation of the R-MgBr somehow....

Do you know of a detailed listing of different ethers used in the Grignard rxn and their respective yields? 

How about your interpretation on ultrasonic Grignards..??  How does this work if water is present??  Does the ether carry away the water as an azeotrope during sonication?

thanks
xoxo!!!!
Julia
 
 
 
 
    PolytheneSam
(Master Searcher)
03-27-02 04:52
No 288390
      grignard.notes.html  Bookmark   

See ../rhodium/chemistry /grignard.notes.html


http://www.geocities.com/dritte123/PSPF.html
The hardest thing to explain is the obvious
 
 
 
 
    ChemicalSolution
(Hive Bee)
03-28-02 02:41
No 288778
      high bp ether  Bookmark   

http://www.haltermann.com/product/news/press/highpurity.htm

These folks talk about n-butyl ether in a Grignard rxn..

Any first hand expiriences with the odor of this stuff??
 
 
 
 
    Rhodium
(Chief Bee)
03-28-02 07:14
No 288865
      Bu2O  Bookmark   

Are you talking about how strong the vapor is, or the agreeableness of the fumes?

I know methyl tert-butyl ether smells noticable less than diethyl ether, something like a more "earthy" tone than THF.