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chemrox
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making diethyl ether
I like ether for a lot of things including extractions and Grignards. It's become hellishly expensive and I'm planning to make it in the lab. One of
the issues is the ethanol we start with .. the cheaper stuff is quite dry but denatured with methanol. Doesn't this mean that methyl-ethyl ether and
dimethyl ether will also be formed and if so do I need to be concerned?
Second issue is water formed in the first step yielding ethyl-H-sulfate and water. I think its assumed the acid will pick up the water but could I
improve yield by running a Dean Stark during the process?
I could reflux the first acid/ethanol mixture under the Dean-Stark until I got the water out and then rig for distilation and addition of the second
round of ethanol. The question is: is the amount of water to be taken out significant or is it trivial because of the acid? I need the final product
to be dry and count on having to treat it with Na before using it in the Grignard reax or metal hydride reductions.
I searched the forum for this kind of discussion and didn't find any but I've failed to find relevant material before. So if there's already a thread
I could have read on this please accept humble apologies.
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Antwain
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dimethyl ether bp.-23*C, methyl ethyl ether (methoxy ethane) bp.8*C
pretty sure you don't need to worry about dimethly ether. that will be lost readily even form diethyl ether.
methyl ethyl ether is probably more likely to stay in your diethyl ether unless you fractionate it.
question is does it matter if you are only going to be using it as a solvent? I imagine that if it wasn't so volatile, methyl ethyl ether would be a
perfectly practical solvent for such things as Grignards.
As for the practical method of making ether, I have no experience, but you will probably get some ethylene as well, and you don't have to worry about
that either bp.-103*C
When I say you don't have to worry about these things... you do if you have a flame anywhere nearby 
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Sauron
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Christ, not just that. Explosion proof electricals and lighting throughout. Ether fumes are heavier than air and tend to accumulate low as a result,
so do this in a well vented tested hood also ex-proofed.
There is lots of detail in Ullmann and Kirk-Othmer on ether manufacture. But I think it is foolhardy.
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smuv
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How much ether are you looking to produce? Having synthesized ether once before from sulfuric acid and ethanol (using an admittedly half-ass setup
ie. syringe instead of dropping funnel...etc) it was not worth the time. I would recommend distilling ether from starting fluid, $12 gets you over
500ml of ether. Read the msds' as not all starting fluids are created equally, make sure to find one with a CO2 propellant instead of an isobutane or
propane propellant. With a decent column 1 distillation should yeild a pure product...but sometimes I feel it is faster to rush a distillation, and
then subject the distillate to yet another fractionation, to get a very pure product in a similar span of time.
It also may be possible, to extract the ether from heptane, through an extraction with a concentrated HCl solution....but I haven't tried this method
as it looks kind of messy...but I thought I would point it out.
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Antwain
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Ahhh, the good old "start ya bastard" extraction
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Slimz
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http://www.sprayproducts.com/starting-fluid.php
They claim 60% ether, im not sure of the propellant
john deer starting fluid is said to conatin 80%
Prestone is prety high too and more widely available.
[Edited on 27-9-2007 by Slimz]
Johnny was a chemist’s son, but now he is no more. What Johnny thought was H2O was H2SO4
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smuv
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Prestone...looks high based on msds...but It is at the lower level from what is claimed...6 cans of prestone premium starting fluid will yeild around
600-650ml Pure ether. 6 cans is about...3/4 of a gallon. I will admit I have never taken the distillation to total completion...because after a
certain length of time I always get bored of having to babysit the ether still (definitely not something to leave unattended) and also...there is the
factor of diminishing returns...
P.S. I throw the left over heptane into my car...it doesn't knock....even when run with 'regular' gasoline....not that I recommend it. It reduces
(duh) the range per tank by about 30 miles...but it is the best way I can think of of disposing of large quantities of heptane.
Hehe @ antwain I dont know how it makes my car start faster when it makes me so sleepy.
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chemrox
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@Sauron
Why is making the stuff more hazardous than distilling or for that matter refluxing it? ala Grignard for example? Seems like some of the suggestions
made here, useful as they are, would be in the same ballpark volatility speaking .. we have a pilot light in the basement I think I'll shut off.
I wanted to be sure and thank all of you for the information and advice. If I don't use it today, I'm sure to sometime. Any data on peroxides in the
OTC's?
[Edited on 27-9-2007 by chemrox]
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pantone159
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| Quote: | Originally posted by smuv
P.S. I throw the left over heptane into my car...it doesn't knock....even when run with 'regular' gasoline....not that I recommend it. It reduces
(duh) the range per tank by about 30 miles...but it is the best way I can think of of disposing of large quantities of heptane.
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FYI - n-Heptane has, by definition, a zero octane rating. (It burns poorly.) However, most modern cars can handle low octane fuel, by automatically
adjusting timing. (Which does hurt performance/mileage/etc.) But since you aren't completely filling the tank with the stuff, it is diluted with
decent octane rating gas, and so probably works out ok.
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smuv
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they are inhibited with bht...but of course when you distill it you lose this protection.
I have never had peroxide related problems during the distillation of starting fluid, largely because of the fact it is inhibited and it is not
distilled to dryness because of the remaining heptane. After I finish distilling the ether I throw in a loop of copper wire (as I think I read a
while ago that Cu(II) decomposes peroxides, yet catalyzes their formation). I usually distill ether as needed, and only very rarely store it for more
than a week. I am cheep however as BHT is readily obtainable from health food stores and internet retailers (it is apparently an OTC herpes
treatment). Good luck...
@ pantone159 I am aware that heptane has a 0 octane rating, before I ran it in my car, I would just burn it as I am speaking of large quantities of
heptane more than I can save as a cheep non-polar solvent. Burning it in my car while stupid as it lowers my fuel economy just makes me feel less
guilty about wasting the heptane.
[Edited on 27-9-2007 by smuv]
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Antwain
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@chemrox
If the stuff is sealed in an aerosol can it wont have peroxides, I think you can say that pretty much for certain as it would be much too dangerous if
they did. Just don't let it out and then wait for a week before distilling it.
Also, I really, really wouldn't do this indoors unless you have a fume hood. You will condense most of it with cold water, but not all, and the rest
will form a nice explosive partition building up from floor level. Its really nasty how easily it forms explosive mixtures with air and IIRC the min
explosive limit is ~2% so basically not much at all. A basement is probably the worst place I can think of to do an ether distillation in.
@smuv
seems like a shame, i could use a few litres of n-heptane 
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smuv
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Oh, I meant to comment about safety. I know some people might flame me, and I know I am bringing it upon myself, so flame away. I think that
everyone exaggerates the flammability of ether...there I said it.
I used to do distillations outside, taking into account every precaution in the world. 2 years and maybe 2 dozen distillations later I do it in my
basement without much worry so long as the basement window is open. I used to distill ether in a water bath but heated by a griddle controlled by a
bimetalic strip thermostat, and have never had problems. Once I controlled the distillation with a variac but used a heating element that wasn't
designed for constant duty, I noticed that the temp at the top of the column was acting really weird, and seemingly not "listening" to my variac, then
I smelled something funny (not ethereal) and noticed that the element was glowing bright red in one spot and a pool of metal was oozing out of the
heating element; although i sweated bullets I had no fire.
There are 3 things that I think if you follow you will never have problems.
1. Use a big water bath with high walls (I use a big kettle)
2. Use a really efficient condenser (I made one out of 2 concentric copper tubes and 2 copper pennies, copper condensers are much more efficient than
glass)
3. Cool the distilled ether with pleanty of ice.
If you have a vacuum adapter I suggest you you connect a hose to it and route the hose out a window, that helps a bit too keep down the smell.
I am not trying to say distilling ether is a safe practice; I know it is a little risky. And I reacognise that maybe I have just been lucky with my
experiences. However I also feel like people make ether out to be the devil, where as I find it to be a very convenient solvent. It has a low
boiling point and is not very toxic, win win in my opinion.
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Antwain
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To be honest I cant disagree with you. I once tried to make something like a Molotov with ether and a 50mL vial. I threw it against a wall and it went
out. But I nearly lost my eyebrows when I went in with a lighter. If you have ever seen the demonstration with a several meter trough and a candle at
the bottom you can never relax too much around ether though.
I think that the biggest worry is that a little ether can make an explosive concentration in so many cubic meters of air, so that if it ever does
ignite, your house blows up.
[Edited on 28-9-2007 by Antwain]
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smuv
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In my earlier days, I used to completely submerge the receiving flask in ice water, and rigged a hose out of the flask so the pressure would equalize
above the ice water. Once after I finished distilling the ether, I removed the flask and found it to be half full. In the process of disconnecting
the flask I did not notice any ethereal odor. I then inhaled deeply through my nose about 6 inches above the flask, and only was met with a faint
ethereal smell. I thought there was a leak in my apparatus and the flask had filled with water or something crazy (my thinking makes no sense as
ether and water are imiscible, maybe I remember my reasoning wrong). I was frustrated, so as I final test, I lit a butane microtourch and passed the
flame a couple of times right over the mouth of the bottle containing ether; It did not ignite. With that I loosely corked the bottle and proceeded
to put away my equipment. As i was almost finished putting my equipment away, I heard a pop and saw the cork launch in the air from the bottle. As I
inspected the bottle, I notice a SHARP smell of ether. As the ether warmed up and its vapor pressure almost quadrupled the loosely fitting cork was
shot out of the bottle, which indeed did contain much ether. Long story short cold ether ain't so dangerous (although I will admit at first my
distillations were sloppy and probably had a 10% heptane contamination which would decrease the vapor pressure).
Anyhow I am ether ranting.
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chemrox
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I got a set up to run it and decided to move the operation to a special bench I made for doing things outside. It has a water supply line with a
water pump and outlet for condensers and an electricity strip. When we finally get our hood made it would be safe to do in that. We designed it with
vapor removal on the bottom sides and top. My partner insists on explosion proof fans but I think that's over the top for ether as long as the
throughput is high. Hydrogen might be another issue and we will have H2 evolution later on.
I wasn't thinking:
"If the stuff is sealed in an aerosol can it wont have peroxides, I think you can say that pretty much for certain as it would be much too dangerous
if they did. Just don't let it out and then wait for a week before distilling it."
Of course!
@ Smuv
"Use a really efficient condenser (I made one out of 2 concentric copper tubes and 2 copper pennies, copper condensers are much more efficient than
glass)"
Please elaborate that construction for me if you would. But tell me, how do you monitor the vapor column?
I used to reflux 10L of ether in a 22L rb and I used a condenser with a jacket and cold cold-finger. The vapor column never got very high. The lab
still stunk of ether though .. mostly from being present in 5 gal drums. I wish I could get 5 gal drums now without spending the GNP of Lichtenstein
to get them.
[Edited on 27-9-2007 by chemrox]
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smuv
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The condenser I am talking about, basically a west condenser made out of copper. A big pipe with 2 end caps (Cu pennies) soldered on, and a hole
drilled in each end cap and a smaller tube inserted and soldered in. Then 2 hose bungs are added (Just use some scrap copper tubing from the inner
tube of the condenser). Bam! you just made a copper condenser which will outperform any glass one of equivalent length.
| Quote: | | But tell me, how do you monitor the vapor column? |
A thermometer.
When distilling or refluxing ether, even if you get it really cold, the ether still evaporates and stinks up the room (if you aren't in a hood). In
situations like that, it is best to put a vacuum adapter on top of the condenser and route a hose from the adapter out a nearby window.
I don't understand why you were using a condenser and a cold finger; if I am understanding correctly, you are creating a closed system, which could
easily shoot the cold finger out of your condenser. Or worse if your cold finger fits tightly, your condenser off of your flask.
p.s. With the quantities of ether you are dealing with, be safe. One thing is to have a fire with 1 liter of ether, it is another when GALLONS of
ether are involved.
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chemrox
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No no no no! The condenser construction: a regular jacket and inside a coiled coldfinger integral with the jacket - there's a name for this beast ..
it's a lot like the one on my rotovap. (See .. I've got all the stuff but my technique still sucks!) I'm working on it with things like this for
practice. Notice Vogels say the diethyl ether syn is not suitable for student experiments and I see why.
I may not sound like it all the time but I'm the boss here. Sometimes chief bottle washer too. So today as an example of what happens sometimes, I
was making my ether .. trying to make 100 ml or less. So I've got everything set the way I want it. Addition funnels is raised above the boiling
flask with a few adapters to get the connection between the pour stem and the tubing out of vapor's way. It works perfectly! And I mix the acid and
alcohol and set the flask back in the setup. Here's what happened- the phone rang with a guy trying to get out of having to pay. So by the time
I've got him convinced to pay the reaction mixture is already over 160 deg and climbing. I add alcohol and everything seems OK. Then wife comes by
.. seems I was supposed to take the dog to the groomers. Fuck!! So I pull the mantle off and lower it out of the way and take off with the dog.
When I get back the mixture is under 100 (it's black since starting to cook). I crank it back up but it goes way past 140-150 (the limits for the
exp.) to about 175 before the product starts coming over. I collect another 20-30 ml and shut it all down. I don't like what I'm seeing or smelling.
The smell was originally alcohol and ether .. now there's something acrid and somethings sweet mixed in.
I salvaged the unused alcohol. Set the product aside for when the IR supplies get here. And dumped the reaction mix, putting the dirty glass into
the cleaning bath. I'm wearing a face shield the whole time. This is a fucking disaster and fairly typical of what happens when I get distracted.
This is not a reaction to interrupt or leave by itself.
So what was I making during the second phase? Judging from smell and ingredients: ethyl acetate and acetic anhydride. In ether of course.
I vow to henceforth not start a process when my wife is free to come by and not pick up the phone while I'm working. It's like driving and talking on
the cell phone. You can't give proper attention to driving while you talk if you're the least bit visual as I am.
Anyway-I'm pissed. This is a simple fucking converison of alcohol to ether and I've blown it. No A for this lab! I've also learned a valuble
lesson. I recount it here that someone else may read and heed to his benefit. I'm also seeing the wisdom and biting the transportation cost bullet
and paying the freight, literally, ot buy the stuff in gallon containers. I also see the wisdom in buying tech grade ether. I'm going to have to
distill it anyway. Ether still here I come. I really need that hood!
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evil_lurker
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Here is the setup I was using to make ether... I've now graduated to a heating mantle, new table, and frame but the setup is the same.
Now then, unlike my pic which was more or less a trial run, pack your hempel column.
The actual procedure is pretty easy to do, simply fill with ACS grade sulfuric acid to approx 30% of the volume of a two or three neck flask. Add in
an equal portion of everclear (preferably molecular sieve dried.. not necessary but will give you more bang for the buck).
By the end of the addition it should be fairly hot. Turn on the heat. You will see that ether will start to be produced once the sulfuric acid/ethanol
mix hits around 115ºC. Soon as it the ether starts coming over, open up the addition funnel dropwise.
Try to adjust the heat and flow to where the very top of the hempel column is almost too warm to touch... if it gets too hot, that means you got
significant amounts ethanol coming over. There really is no need for a thermometer at the distillation three way adapter. And oh yeah, it helps
greatly if you put a fan on the column.
In my method, the sulfuric acid is not acting as a catalyst, but rather as a dehydrating agent because the water formed is bound up. As such the acid
gets "spent" requiring more and more heat to be added to maintain output. I find that ACS grade sulfuric is good for 3-4 volumes of alcohol. One could
possibly push things further with an adapter that drops the ethanol below the surface of the acid and a longer hempel column or water cooled column.
Not all chemicals are bad. Without chemicals such as hydrogen and oxygen, for example, there would be no way to make water, a vital ingredient in
beer.
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chemrox
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Oustanding!
I have a few questions and I should photo the setup I was using for you but first let me ask:
1) the hemple column- I could sub in any fractionating column right? what is it helping you separate out? ethanol .. acetate? .. both?
2) In the procedure I was following (until the fucking phone calls etc.) mandated running the ethanol below the surface of the organosulfate H2SO4
mixture. I take it you dispensed with that as unecessary? and you didn't use a stirrer in place of it either? I have a condenser like that but it
has 29/32 joints and I was using the converters to buy some distance to attach the tubbing to the addition funnel tip. Long story .. goes with the
Vogel's instructions I was trying to be scrupulous about. I really like keeping the ice in a cooler like that. Looks like you were in the garage
with the furnace (?) I see tubing from the vacuum adapter. Out the window? neighbors? or down the sink with the water .. what i did.
I just re-read and edited.
You didn't go subsurface with the alcohol but feel you might improve yield by doing so. I'm going to send my condenser up to the glassblower and have
the tapers changed to 24/40 to match everything else I use.
I have a number of 29/32 female 90 degree adapters with long tubes if you or anyone you know can use 'em. They came with my addition funnels from an
ebay buy. anyway, I've got some fractionating column choices. I wasn't clear on that. In the usual way you might insulate the columns or even heat
them to the same temp as the takeoff liquid. Is that something you might do to improve separation? Did you then wsh the product with NaOH? I
realized after I'd placed it that the drying tube was pintless as I would have to wash the ether to get rid of acids and any oxides.
Did you get any ester formation or was that the result of my overheating?
What do you predict getting from too much heat? Was glassware cleanup an issue?
[Edited on 28-9-2007 by chemrox]
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evil_lurker
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| Quote: | Originally posted by chemrox
Oustanding!
I have a few questions and I should photo the setup I was using for you but first let me ask:
1) the hemple column- I could sub in any fractionating column right? what is it helping you separate out? ethanol .. acetate? .. both?
The column helps to seperate any unreacted alcohol which then refluxes back down into the flask. I'd say 300mm is minimum
with faster results being gotten from a 400-500mm column due to increased reflux ratio.
2) In the procedure I was following (until the fucking phone calls etc.) mandated running the ethanol below the surface of the organosulfate H2SO4
mixture. I take it you dispensed with that as unecessary? and you didn't use a stirrer in place of it either?
Yup, works just fine to just drop it on top... you can actually see the drops floating around on the surface dancing around
and shrinking. I think Vogel was wanting a catalytic reaction in which the alcohol is quickly converted and distilled over along with the water. And
yeah, a magnetic stirrer makes things go much more smoothly... in fact I believe it is necessary to equlibriate the acid/heat/mixture.
I have a condenser like that but it has 29/32 joints and I was using the converters to buy some distance to attach the tubbing to the addition funnel
tip. Long story .. goes with the Vogel's instructions I was trying to be scrupulous about. I really like keeping the ice in a cooler like that.
Looks like you were in the garage with the furnace (?)
Nah its an old shed out back used for storage. It was built a long time ago by my grandfather who used to smoke hams in the
back. The picture best I can remember was takin while it was still fairly hot outside... daytime temps around 90ºF best I can recall I was going thru
about 40lbs of ice in a period of 6 hours just to make a liter... most of it was melting due to ambient heat absorbed from the condensor lines and on
the outside of the condensor... I imagine with some foam insulation on the cooling lines efficiancy could be increased 30% or so.... it might not hurt
to switch over to neoprene either.
I see tubing from the vacuum adapter. Out the window? neighbors? or down the sink with the water .. what i did.
Out the freaking window. Had a rather large fan behind me blowing air in from the opposite direction. With the ice in the
condensor and ice and the cooler you could sniff the vent line and not even get a buzz. Nearest neighbor is about a quarter mile away so no smell
issues.
I just re-read and edited.
You didn't go subsurface with the alcohol but feel you might improve yield by doing so. I'm going to send my condenser up to the glassblower and have
the tapers changed to 24/40 to match everything else I use.
You can buy one off of ebay just like the one in the pic for $70 or so from kantu200 IIRC... personally that is about the
only thing I would buy from them because IMO it isn't exactly the highest quality glass out there, but you can't beat the price on a condensor like
that as a similar one would cost over $200 from just about any of the major glass manufacturers in the USA... the condensor in the pic is 400mm long
and with ether it just about needs every bit of it. If you want a sub surface adapter, you can get one from expediglass cheap.[/red]
I have a number of 29/32 female 90 degree adapters with long tubes if you or anyone you know can use 'em. They came with my addition funnels from an
ebay buy. anyway, I've got some fractionating column choices. I wasn't clear on that. In the usual way you might insulate the columns or even heat
them to the same temp as the takeoff liquid. Is that something you might do to improve separation?
You want to COOL the column to increase seperation.. Ether has such an insane partial vapor pressure it'll come right over
when the top of the column is just warm.
Did you then wsh the product with NaOH?
Actually you can put some NaOH solution in the reciever flask... that will save you a washing step later on... then hit it
with an equal volume of fairly concentrated pre-made and ice cold CaCl/H20 solution... that will rid it of the alcohol and quite a bit of the water
since CaCl forms an addition product with alcohol... finally, sprinkle in some oven dried CaCl, let sit for a few hours under ice and distill directly
from that. Peroxides should be undetectable at this point so you can go close to dryness.
I realized after I'd placed it that the drying tube was pintless as I would have to wash the ether to get rid of acids and any oxides.
Did you get any ester formation or was that the result of my overheating?
Nope, nada... well I take that back.. you do get some EtHSO4 in the spent acid, but other than that there should be no
esters formed since there is no acids going in other than the sulfuric. Even if you did somehow create ethyl acetate or whatever, the esters would not
be able to come over with the fractionating column in place. My guess is you used sulfuric acid drain cleaner which has god knows what all in it...
use only ACS grade sulfuric for best results.
What do you predict getting from too much heat?
Well supposedly ethylene gas.
Was glassware cleanup an issue?
Yes, very much so. Back then I was using joint grease. That shit is a total pain in the ass to remove and contaminates
everythign. I switched over to teflon joint sleeves, and they work much much better... other than that, just rinse with water and mild detergent like
simple green... hell the acid starts out clear and when its done is slightly tan.
[Edited on 28-9-2007 by chemrox] |
Hope that answered your questions.
Not all chemicals are bad. Without chemicals such as hydrogen and oxygen, for example, there would be no way to make water, a vital ingredient in
beer.
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smuv
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Oh, a note. If the acid alcohol mixture turns reddish during the process of the distillation, it is fine, it just means that the ethanol has been
denatured with some ketones.
I do not think you made any acetic anhydride or appreciable amounts of ethyl acetate. I think you probably made some ethylene though, which if I
recall does not smell yummy. I also do not think stopping this process in the middle would appreciably diminish your yields. So I would look further
into your technique/procedure.
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Fleaker
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Actually ethylene smells sweet. The acrid smell is probably dilute amounts of a sulfide of something (if you used cheap sulfuric drain cleaner, this
is common). IIRC, isn't anything warmer than 170C sulfuric acid temp. prone to formation of ethylene?
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
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smuv
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The Dutch chemists first made ethylene by heating ethanol in sulphuric acid to 150-160 degrees. They also reported that even after washing the gas
with water and ether it had a very choking smell.
--Ethylene and its industrial derivatives by Miller
According to wikipedia though, it has a sweet smell.
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Fleaker
International Hazard
Posts: 1252
Registered: 19-6-2005
Member Is Offline
Mood: nucleophilic
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I am reporting from what I personally experienced that it smells sweet. It does to me, it does to my coworkers, and I am positive that it smells the
same in the Netherlands as well! I like the smell of C2H4 and have smelled it many, many times and its sweet odour remains the same  .
As I said, that chocking smell is probably due to impurities in the sulfuric.
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
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smuv
National Hazard
Posts: 842
Registered: 2-5-2007
Member Is Offline
Mood: Jingoistic
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I wasn't disagreeing with you, I was just pointing out, that the original group of chemists that made ethylene observed that their product had a
chocking smell. This is why I also inserted the tidbit about wikipedia.
Although looking back on it, I understand I did not really convey my thoughts clearly, I merely quoted 2 sources and left you to interpret what I was
trying to say.
Sorry for the confusion.
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