Esplosivo
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Long chain ether syntheses
Ethers are very good solvents, and very important (or essential) in 'solvent extraction' separation techniques. The most common ethers
though, such as methoxymethane and ethoxyethane are highly volatile, and may result in dangerous, highly fammable gasses.
I appreciate some suggestions on the syntheses of long chain ethers, which should have a moderate boiling point. The chemicals used need not be
commonly available  . Thanks
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chemoleo
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Best for starters would be ethylenoxide... which readily polymerises. Chainlength can be varied with reaction conditions 
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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Esplosivo
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I made some search on google and I didn't find any good info about this ethylenoxide. Could you please provide me with a formula for this
chemical, and how the ploymerization takes place. Btw, does the polymerization take place under increased pressure and high temperatures? If so I
would like something more simple then that.
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chemoleo
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Lol, it's because I didn't take care of spelling, thought it was evident it is called ethylene oxide.
Check http://www.cefic.be/sector/eodsg/guide9701/eo01.htm for starters.
Ethylene oxide can be of course used in combination with other chemicals, so more specific ethers can be produced than just a random polyethylene
glycol polymer.
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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Esplosivo
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The process is feasable. The only damn disadvantage is that ethylene oxide is a gas at rtp! That will complicate matters. Right now I am trying to
find out how the syntheses is carried out. Maybe the gas can be created and polymerized in situm. Do you have any suggestions on how this can
be synthesized, since being a 'toxic' gas I will surely not be able to buy it 
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vulture
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Ethylene oxide is not only extremely toxic, it also poses an extreme explosion hazard because of it's VERY wide explosion range in air.
Furthermore, Ethylene oxide has been researched as a CW, because it's also a blistering agent.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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Esplosivo
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Yeah, that is nice to know lol. Well maybe the reaction is not 'perfect' after all. I don't think I can handle such a compound at my
home lab. Are there any other possibilities of long chain ethers which have a moderately high boiling point, such as certain glycol ethers? Glycol
ethers are surely were good solvents, but if I am correct these may be soluble in water, though I am not sure. Most of these glycol ethers require
compounds like propylene oxide for their synthesis, which are also toxic.
[Edited on 18-3-2004 by Esplosivo]
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BromicAcid
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How long an ether chain are you talking, I had a thread that I recently discussed on Symetrical polyethers maybe you should go take a look at that.
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Esplosivo
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Thanks for the input. I was thinking about some ether having a volatility of approximately that of pentyl ether (pentoxypentane), which is around 180
deg. Celcius. In this way the ether could still be evaporated from a mixture, but it would not evaporate at rtp like ethyle ether.
I'll check the forum for symmetrical polyethers. At a quick glanc I've noticed the mentioning of ethylene oxide, which I was discouraged to
use (thanks vulture).
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unionised
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Ethylene oxide polymers (also known as polytethylene glycols) are generally solids and disolve in water. they wouldn't work as extraction
solvents.
You might want to look at methyl tertiary butyl ether, made in multi ton quantities as a petrol additive so it's relatively cheap.
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Esplosivo
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Thanks for the suggestion. Tert-butyl ethers can be prepared by the addition of equimolar quantities of an alcohol to isobutene, with a catalytic
amount of conc. H2SO4 right? Therefore the reaction for the synthesis of methyl tertiary butyl ether would be the as the one below:
CH3OH + CH2=C(CH3)CH3 --> CH3OCH3(CH3)2CH3
The equation states that methanol is added to isobutene to form methyl tertiary butyl ether. Conc. H2SO4 is added as a catalyst.
Can anyone verify is this synthesis is correct. And how much H2SO4 should be added (should there be an excess?! so that water is removed - if water is
present the reaction is reversed and the ether is changed back into its constituent molecules, so I have read).
Is methyl tertiary butyl ether a gas?! I have found that bpt is -50 deg celcius at 760 mm Hg (i.e. 1 atmp.)!!!!!!!!!! If this is so then the alcohol
should be a longer one so to increase the mass and length of the molecule to increase the bpt.
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unionised
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If your acid, methanol and isobutylene are dry then there isn't any water to spoil things.
MTBE is a liquid, BPt 55C (and I would like to think I wouldn't be dumb enough to point out that you can't use a solid ether as an
extraction solvent; and then sugest using a gas).
IIRC isobutylene is a gas which could make life awkward.
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