jwarr
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diethyl ether
Diethyl ether is a really handy solvent to have around the lab, but it seems the DEA thinks its only use is in the manufacturing of drugs. I'd love
to get some suggestions on how one can distill/synthesize Et2O from commonly available materials. Also, what precautions should be taken when
handling/storing this stuff?
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bfesser
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There has been plenty of discussion on this compound/solvent on this forum already--especially regarding its synthesis. Please use the search
function.
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ammonium isocyanate
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Diethyl ether is very, very flammable and tends to form explosive peroxides. As such, it must be handled with extreem caution and it is not advisable
to keep large quantaties lying around.
Distilling it is difficult and hazardous. However, if done carefully one can avoid a fire.
I have tried synthesizing ether for use as a solvent, with little success. I did get some ether, but at 5% of theory .
My procedure was as follows:
Add 50mL of ethanol to a 500mL Florence flask. SLOWLY (I made that mistake) add 20mL of conc. sulfuric acid. Attatch a condenser with a 250mL
Erlenmeyer flask at the other end. Make sure all seals are tight and place on a burner. Heat very carefully so that about 2 drops distill over per
second. After the rate of distillation falls to about .5 drops per second (never turn up the heat), turn off the burner. Wash, filter (if necessary)
and seperate in a seperatory funnel with the following, in order: 50mL 10% KOH solution, 50mL 75% saturated NaCl solution, 35mL 75% saturated NaCl
solution. Shake with 5g of CaO to free from water, then filter. Yield of ether was 2.1mL, density approx .79g/mL.
Theories to improve yield:
1. Use pure ethanol instead of denatured alcohol (I was too lazy)
2. Increase the quantaties involved to decrease losses with washing
3. Don't live at 9300 feet
4. Distill a little slower
5. Use a fractionating column (I don't have one)
Feel free to give it a go, but it might be easier to look around for a supplier. And if you do, keep a fire extinguisher nearby just in case.
For future notice, try using the search engine or looking on google/wikipedia before starting a new thread about a topic. You're new, so I'm
answering your question, but posting a question without searching is a bad habit to get into.
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jwarr
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Quote: Originally posted by ammonium isocyanate  |
Feel free to give it a go, but it might be easier to look around for a supplier. And if you do, keep a fire extinguisher nearby just in case.
For future notice, try using the search engine or looking on google/wikipedia before starting a new thread about a topic. You're new, so I'm
answering your question, but posting a question without searching is a bad habit to get into.
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My apologies, perhaps I should have been a bit more forthright. I have seen the Et2O from ethanol synthesis on Rhodium, I was hoping there was
perhaps a less dangerous procedure. As for searching here, the closest posts I found were about brewing ethanol. Perhaps I'm not searching using the
proper terms?
As for getting it from a supplier, I don't like the idea of being on a DEA watchlist for purchasing a List II chemical, regardless of my intentions.
[Edited on 23-7-2009 by jwarr]
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ammonium isocyanate
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An alternative procedure that comes to mind which I've never tried would be reacting sodium with pure ethanol to yield sodium ethoxide, then pumping
in ethyl chloride gas (generated by reacting ethanol with HCl in the presence of ZnCl2) to a solution in toluene. Of course, this uses up alot of
precious sodium.
An alternative synthesis I read about at http://www.springerlink.com/content/vxv40v3t0458v02x/ requires the use of zeolites as dehydrating agents and 10-30 mol% ethyl iodide (search for
iodomethane on this forum for an analogous synthesis). It is carried out at a temp of 160-200*C, so there is still a real fire danger.
What do you plan on using the ether for? It is possible another solvent might work just as well or better for your purposes.
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jwarr
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Nothing in particular, it just seems like a handy non polar non-water soluble solvent to have around. I guess I could always use DCM.
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Formatik
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| Quote: Originally posted by ammonium isocyanate |
My procedure was as follows:
...
Theories to improve yield:
1. Use pure ethanol instead of denatured alcohol (I was too lazy)
2. Increase the quantaties involved to decrease losses with washing
3. Don't live at 9300 feet
4. Distill a little slower
5. Use a fractionating column (I don't have one) |
6. Don't use a burner. Basic organic chemistry rule is not to heat the flask with a direct flame if the substance is flammable. If you had done that,
then it wouldn't have decomposed to ethylene (which is what happens if you heat over about 130-140 deg., autoignition point of ether is not far off
and depending on the cooling and air content it will or won't ignite).
7. Monitor the temperature closely with a thermometer. Best yields have been reported when temperature was 140-145 deg (Prescot, Am. 6, 243; Peter,
Ber. 32, 1418). Above that the yield sinks. At 160 deg. a lot of SO2 forms. Ethylene and SO2 are the main side-products, though there are many more.
No need to make it worse than it is.
8. Some FeCl3 or SnSO4 addition can also increase yield a bit (Oddo, Gazz. chim. Ital. 31 I, 316).
| Quote: Originally posted by jwarr | | My apologies, perhaps I should have been a bit more forthright. I have seen the Et2O from ethanol synthesis on Rhodium, I was hoping there was
perhaps a less dangerous procedure. |
There are other ways to form ether, but this old method is probably the most simple. Phosphoric and arsenic acids are also able to convert alcohol
into ether like sulfuric acid. Though with phosphoric acid you might want to whip out the platinum retorts, since it attacks glass when hot.
| Quote: | | As for searching here, the closest posts I found were about brewing ethanol. Perhaps I'm not searching using the proper terms?
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Et2O is very common molecule so it is going to take quite a bit of digging. Though I can think of at least two threads that would have answered some
of your questions. Len's illustrated guide of ether in the prepublications section. And then this thread about some of the saftey: http://www.sciencemadness.org/talk/viewthread.php?tid=10380 (there are probably a couple of these type of threads).
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Phosphor-ing
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If you can perform fractional distillation, then starting fluid is the way to go. If not you're playing with fire synthesizing ether.
No pun intended
"The nine most terrifying words in the English language are: 'I'm from the government and I'm here to help.'" -Ronald Reagan
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starman
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You didn't search very hard.Check out Len1's illustrated guide in prepublication.Detailed step by step with photos,closely adhere to instructions
given and you can't go wrong.....then again....
Chemistry- The journey from the end of physics to the beginning of life.(starman)
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bfesser
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Ammonium isocyanate, three notes:
1. You should have chilled your receiver in a water ice/salt slush.
2. 75% is a concentration, not a 'saturated' solution. Saturated means that no more will dissolve under given conditions (temperature)--Google for a
more precise definition. Saturated NaCl used as a drying agent during extractions is also commonly simplified to 'brine'.
3. Also, why did you use a 500 mL flask to boil only 70 mL?
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ammonium isocyanate
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bfesser, three responses:
1. I did but forgot to mention it in my earlier post.
2. 27g of NaCl was added per 100mL of water, whereas a saturated solution at 22*C is approx. 36g per 100mL. I didn't have my notes on hand, at that
was the tidbit of information I happened to remember.
3. It was the only size Florerence flask I had.
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JohnWW
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There are other ethers, of comparable molecular weight, that can be substituted for diethyl ether, such as tetrahydrofuran, oxane (pyran), and
dioxane. Because of the volatility and low boiling point of diethyl ether, you could also look at ethers of higher molecular weight, such as dipropyl
ether, diisopropyl ether, dibutyl ether, and di-tert-butyl ether, which would be made in a similar manner to diethyl ether (which BTW utilizes ethanol
which unless adulterated is expensive because of the excise tax on it).
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UnintentionalChaos
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| Quote: Originally posted by JohnWW | | There are other ethers, of comparable molecular weight, that can be substituted for diethyl ether, such as tetrahydrofuran, oxane (pyran), and
dioxane. Because of the volatility and low boiling point of diethyl ether, you could also look at ethers of higher molecular weight, such as dipropyl
ether, diisopropyl ether, dibutyl ether, and di-tert-butyl ether, which would be made in a similar manner to diethyl ether (which BTW utilizes ethanol
which unless adulterated is expensive because of the excise tax on it). |
The use of diisopropyl ether is strongly discouraged as it develops peroxides much faster than ordinary Et2O.
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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497
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| Quote: | | An alternative procedure that comes to mind which I've never tried would be reacting sodium with pure ethanol to yield sodium ethoxide, then pumping
in ethyl chloride gas (generated by reacting ethanol with HCl in the presence of ZnCl2) to a solution in toluene. Of course, this uses up alot of
precious sodium. |
I believe there are better/cheaper ways to sodium ethoxide, so save your Na metal. Dissolving NaOH in ethanol and then forcing the equilibrium toward
sodium ethoxide by dehydrating it with a zeolite works IIRC. There's a thread on the forum somewhere about it. From what I remember it looked pretty
easy. And ethyl halides are easy, so that might be an interesting route that avoids high temperatures... Maybe you could even form the ethoxide in
situ?
[Edited on 25-7-2009 by 497]
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greenyppols
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I did the sulphuric acid/ethanol distillation on my stovetop before I knew any better...ya know, I never thought of the ol' pilotlights.... I used
homebrewed ethanol, which is incredibly cheap, all things considered.
musta been lucky as hell, but no ka-boom...and managed to get 500 ml.
I do not recommend the stove top method. lol. Like I said, I musta been lucky. But in the end, I got what I wanted.
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aonomus
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This gets me wondering about those spray cans of ether for cold-starting diesel engines. Do they add some sort of inhibitor to prevent peroxide
formation? What about a plastic coating on the inside of the can to prevent metal catalyzed ether formation?
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entropy51
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How can
metal catalyze ether formation? Fe and Cu metal inhibit peroxide formation, although Et2O is unlikely to form peroxides when sealed in a metal can
without exposure to O2 or light.
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Nicodem
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That is not particularly relevant ever since all ethers used as solvents come supplied with radical inhibitors.
I always use diisopropyl ether wherever I should use diethyl ether. Personally, I just hate diethyl ether. It only gives me headaches whenever I get
exposed to its disgusting smell. Diisopropyl ether is way less volatile (you can even use it during the summer!), smells way better, does not give me
a headache and does not make me a clumsy idiot from accidental vapour exposure like the diethyl ether can.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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Magpie
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from Nicodem:
| Quote: |
and does not make me a clumsy idiot from accidental vapour exposure like the diethyl ether can.
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Yes, this happened to me once in organic class. A funny feeling came over me and I knew I just had to get outside for some fresh air.
I suppose the advantage of diethyl ether is that it is easier to remove by evaporation. But that's something I have nowdays - a little more time.
The single most important condition for a successful synthesis is good mixing - Nicodem
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mr.crow
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I thought diisopropyl ether forms solid peroxide crystals inside the threads of the cap!
How about MTBE? Is that as good a substitute as my textbook says?
Grignards only work with ethyl ether or THF. For extraction you can probably use different solvents.
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grind
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| Quote: Originally posted by mr.crow | I thought diisopropyl ether forms solid peroxide crystals inside the threads of the cap!
How about MTBE? Is that as good a substitute as my textbook says?
Grignards only work with ethyl ether or THF. For extraction you can probably use different solvents. |
If you can see crystals in isopropyl ether, it´s too late. Then you should escape, that is work for the explosive ordnance disposal  ...
MTBE is a good substitute, but with slight disadvantages:
- more soluble in water, water is more soluble in MTBE (when I remember correctly)
- MTBE is cleaved in strongly acidic solutions
Advantage: no peroxides are formed.
We often used MTBE, I like the very pleasant smell, and it is very easy to evaporate.
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Neo-6
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This all depends a lot if your goal is just to obtain the ether or to synthetisise it yourself.I personally like making my reagents from scrath
especially if those are watched chemicals but...
In my situation i'm able to buy ether as a starting spray in 400 ml cans that cost 4 € per can (about 6 usd) and this is from local big car parts
store.Of course i cant buy 12 cans at a time without raising suspicion but as of my empirical experience and what i have read i can say;
Reason for athorities to control selling of ether is production of illict drugs.When you think of huge supermarket style hardware stores, you dont get
the old fashion service and advice, but you can be sure that the cute girl working the cash register most certainly doesnt have degree in
chemistry.Average cashier doesnt even know what chemicals to control.
And as what i estimate, producing ether yourself doesnt really come economical, so i just suggest buying that.
Out of my own curiosity,for the ether synthetisisers, what do you use for the antioxidant preventing your ether from forming peroxides?
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grind
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There are a lot of agents, especially BHT or diphenylamine, KOH pellets or sodium metal are suitable. But I´m afraid there is nothing OTC except
solid NaOH.
Keeping your ether bottles full and avoiding expose to air and light will also help to some extent.
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jmneissa
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As a general rule of thumb I keep my diethyl ether in small quantities per bottle (300ml) and mark the date on the label of when either the ether was
synthesized or bought. To prevent the formation of peroxides I will only use a bottle for one year. After that I throw it away. I have never had a
problem with ether by using this method.
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entropy51
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| Quote: | | To prevent the formation of peroxides I will only use a bottle for one year |
If you make the ether yourself
and don't add inhibitor, you might find it intersting to test it for peroxides after a week or two. You may be surprised at how fast peroxides form
in uninhibited ether. Commercial ether containing inhibitor is of course somewhat less prone to peroxide formation.
Ethyl ether is not usually problematic unless distilled, when the higher boiling peroxides become concentrated.
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