Sciencemadness Discussion Board - Synthesis of Diethyl Ether

Synthesis of Diethyl Ether

skeletal-clown - 29-5-2013 at 01:12

So I'm new here and haven't really experimented with organic chemistry much before (I have a fair amount of inorganic chemistry experience), and have a few questions about the ethanol/H2SO4, synthesis of diethyl ether.
I plan to use OTC methylated spirits (95%+ w/v ethanol), home made (via electrolysis of CuSO4), concentrated sulfuric acid and a simple 24/29 ground glass distilation set up on a sand or oil bath. I plan to follow a similar process to the one described in Vogel's Practical Organic Chemistry.
So I guess my questions are these:

1. I have no dropping funnel, would there be any problems with simply adding all the ethanol at the start of the reaction or pausing periodically, cooling the setup and adding more ethanol?
2. My H2SO4 may have slight copper and/or lead impurities, I can't see how this would affect the reaction, but I am pretty new at this.
3. Are there any tips/pieces of advice you guys can offer?

Thanks in advance for any help!

DrSchnufflez - 29-5-2013 at 01:35

Look in the prepublications section for len1's detailed report on Diethyl ether synthesis.

However ether is not somthing that you make without the proper equipment, it is flammable, biologically active, readily forms explosive mixtures with air and it has a very low boiling point so you need, at minimum a long Liebig with ice water running through it.
I would advise that, at minimum you buy an addition funnel.

woelen - 29-5-2013 at 01:47

I would not worry too much about the toxicity of ether (actually, it is very low), but I would worry very much about its flammability and very wide range of concentration in which it can explode when mixed with air. The ignition temperature of ether also is quite low, a hot mantle could already cause ignitiion if vapors are streaking against the heating element.

The boiling point is 34 C and you need very good cooling, otherwise most of the ether will escape as vapor from your distillation apparatus. I doubt whether a Liebig cooler is good enough. Maybe you need a spiral cooler, which has a much longer travelling path for the vapors.

skeletal-clown - 29-5-2013 at 02:04

Firstly, thanks for your help.
A spiral cooler would certainly be preferable, but in the diagram included in Vogel's synthesis, a liebig condenser appears to be used (also, this is all I have on hand). I plan to run it on salted ice-water and plus, it's winter here. My apparatus has a vacuum/vent outlet through which I plan to scrub excess ether fumes.
I know using an addition funnel would be preferable, but is there any reason all the ethanol can't be added at once?
Diethyl Ether vapors are heavier than air and the heat source will be above any possible leaks.

Lambda-Eyde - 29-5-2013 at 03:37

Quote: Originally posted by woelen

I would not worry too much about the toxicity of ether (actually, it is very low),

I wouldn't worry about dying from diethyl ether poisoning either, but with poor ventilation I would worry about passing out in front of an apparatus that needs a lot of attention.

Quote: Originally posted by skeletal-clown

I know using an addition funnel would be preferable, but is there any reason all the ethanol can't be added at once?

Yes, there is. The reaction between diethyl ether and ethanol at high temperature can produce two different products depending on the conditions: diethyl ether and ethylene. If you look up a lab prep of ethylene you will notice how similar it is to that of diethyl ether, but you will also note the subtle differences.

As others have said, go look up len1's topic in the Prepublications forum. It is an absolutely fantastic post which will walk you through the procedure step by step. If you only have a 20-30 cm liebig I would invest in a spiral condenser for this procedure. You will most certainly use it again.

Also, winter in Australia? Meaning 12 degrees on a cold day?

DrSchnufflez - 29-5-2013 at 03:50

Just to clarify by biologically active I meant its effects on consciousness

In response to lambada-eyde yes, pretty much 12 degrees is accurate for victoria, Australia

skeletal-clown - 29-5-2013 at 04:19

Thanks again guys, I'm pretty new to this and your help is very much appreciated. I've found a rather well priced spiral condenser from a company I've used before, but I can't seem to find a good (AKA, not to crappy and still cheap), addition/dropping funnel. Do you have any suggestions as to where to buy one?
I've read through len1's post several times, It's been my other main reference in this procedure.
As for fumes, I plan to carry this out in a well ventilated/semi-outdoors area.
And yes, 12 degrees seems fairly typical here

EDIT: I've been examining the H2SO4/ethanol production of ethylene, and besides the higher temperature, what else is different? So, I guess what I'm asking, is what conditions favour the production of ethylene and which favour diethyl ether?
If what I've read is correct, I could exclude an addition funnel as long as I kept the temperature of the apparatus to 140 degrees.

[Edited on 29-5-2013 by skeletal-clown]

[Edited on 29-5-2013 by skeletal-clown]

RobertRobinson75 - 29-5-2013 at 04:46

You probably want to keep it well below 140C otherwise you may still be producing some ethylene.

[Edited on 29-5-2013 by RobertRobinson75]

Nicodem - 29-5-2013 at 07:48

Quote: Originally posted by skeletal-clown

I know using an addition funnel would be preferable, but is there any reason all the ethanol can't be added at once?

Please read a few procedures for this reaction. It should be then obvious to you, that it can not work if you add all the ethanol at once. The required reaction temperature is claimed to be about 140 °C and the boiling point of ethanol is way lower.

Magpie - 29-5-2013 at 10:19

This brings up a philosophical point that often bothers me, ie,

One person will take the trouble to develop and write-up a procedure for synthesizing a given chemical. Then others, who wish to synthesize said chemical, but do not have the necessary reagents or equipment, will come to the forum asking if some reagents, equipment, or steps can be substituted, or even ignored! I always wonder if these people think that the procedure writers put these requirements in their procedures just for the fun of it, or to make things difficult. It's as if they want all procedures to be reduced to just water, salt, and jam jars!

Mailinmypocket - 29-5-2013 at 10:59

Quote: Originally posted by Magpie

It's as if they want all procedures to be reduced to just water, salt, and jam jars!

LOL!

chemcam - 29-5-2013 at 11:11

This post should have been made under the write-up and I agree he should have known that you can't add all the ethanol at once but when it comes to the equipment needed there are countless different setups that will get the job done. If you don't have an addition funnel think to yourself, "what else could probably work?"

You can use a long stem funnel or thistle tube instead of an addition funnel in this procedure, but, it is more time consuming. Use a two-neck flask; one neck goes to the condenser and the other just has a stopper, when the time comes to add more EtOH remove the stopper and insert the thistle tube or long stem funnel. Simple as that.

If I were you though I would definitely invest in a addition funnel, LaboyGlass has very cheap, good quality addition funnels.

skeletal-clown - 29-5-2013 at 22:25

Quote:

You probably want to keep it well below 140C otherwise you may still be producing some ethylene.

Alright, will do. I'll keep it at the lowest temperature possible while still having something condense.

Quote:

I have read through several procedures, both here on SM and in several text books. (The SM library is awesome by the way!). As I said, I've never really done much work with organic chemistry so this is all very new to me, I'm learning as I go. I've been doing more research, and I now understand why adding all the ethanol at once would not work (without a large excess of H2SO4), forgive me for asking a stupid question.

Quote:

This brings up a philosophical point that often bothers me, ie,

One person will take the trouble to develop and write-up a procedure for synthesizing a given chemical. Then others, who wish to synthesize said chemical, but do not have the necessary reagents or equipment, will come to the forum asking if some reagents, equipment, or steps can be substituted, or even ignored! I always wonder if these people think that the procedure writers put these requirements in their procedures just for the fun of it, or to make things difficult. It's as if they want all procedures to be reduced to just water, salt, and jam jars!

I would have you know that I am not one of these people. As I believe I've stated, I am wiling to buy new reagents and pieces of equipment when necessary (i.e. the spiral condenser), although if money can be spared, I, like anybody else, would like to do so. Also, in some circumstances, said write do have some steps which are able to be substituted or ignored. One piece of glassware can be swapped for another or a different reagent may be used for a slightly poorer yield. Write ups are simply the author's method and not necessarily the only one. And of course I wouldn't "want all procedures to be reduced to just water, salt, and jam jars!", that would take all the challenge and fun out of chemistry!

Quote:

LOL!

Well that sure contributed to the discussion.

Quote:

This post should have been made under the write-up and I agree he should have known that you can't add all the ethanol at once but when it comes to the equipment needed there are countless different setups that will get the job done. If you don't have an addition funnel think to yourself, "what else could probably work?"

You can use a long stem funnel or thistle tube instead of an addition funnel in this procedure, but, it is more time consuming. Use a two-neck flask; one neck goes to the condenser and the other just has a stopper, when the time comes to add more EtOH remove the stopper and insert the thistle tube or long stem funnel. Simple as that.

If I were you though I would definitely invest in a addition funnel, LaboyGlass has very cheap, good quality addition funnels.

Hi, I'm sorry if this is in the wrong section, I'm pretty new to the whole forum thing. As you can see, I have been considering other options to the addition funnel (

Quote:

pausing periodically, cooling the setup and adding more ethanol?

) And your suggestion of using a two-necked flask is very useful, thank you. Wow, thanks for the link also, their prices are really good! I hope the shipping to Australia isn't too much though

Thanks again, you've been very helpful.

testimento - 10-6-2013 at 03:37

Could you make ether by distilling ethanol over Al2O3 catalyst bed at 900C?

According to

[^ Ethyl Ether, Chem. Economics Handbook. Menlo Park, Calif: SRI International. 1991.]

"Vapor-phase dehydration of ethanol over some alumina catalysts can give diethyl ether yields of up to 95%"

Dr.Bob - 10-6-2013 at 08:45

Quote: Originally posted by testimento

Could you make ether by distilling ethanol over Al2O3 catalyst bed at 900C?

You might if you have an industrial, well engineered setup. Otherwise, you will more likely make a news headline, due to the fire that ensues. Temperatures above 200C are not for home chemists unless they have some experience and a safe place to test the system (outside, away from their and others houses).

Skeletal, I would give similar advice, please try this type of reaction outside first, not inside, as I have seen a number of ether fires, and they are quite vigorous. Inside a fume hood, there is some safety, but doing something like this on a kitchen counter or inside, with limited ventilation, there is easily the potential to build up enough vapors to ignite, and ether vapors burn like gasoline, and can ignite from any trivial spark or even hotplate temperatures. So best to do this outside with a hose or fish water pump for the cooling water. Then, you 1) have better ventilation and 2) if it catches fire, not as bad.

I have done similar work, and have seen a few good ether fires. They grow very quickly out of control.

Lambda-Eyde - 10-6-2013 at 09:43

Dr.Bob: garage chemist has experimented a lot with his home-built high temperature tube furnace. I think this experiment could be performed reasonably safe with a well-constructed apparatus and proper precautions. Flushing with argon or nitrogen, good cooling, maybe flaring off the exhaust... It is certainly doable for an experienced chemist.

S.C. Wack - 10-6-2013 at 16:05

Even if done with all precautions, without the missing details, it's most likely to result in many liters of ethylene. 900C and 95% sounds full of specifics.

Organikum - 11-6-2013 at 04:21

Once I read an article I think it was posted even here by leu, which desribed the dehydration of EtOH by kind of solid acid catalyst made by soaking a carrier with 70% H2SO4 at far lower temperatures in a heated tube. Less then 150°C IIRC far less. Good yields.

No time to search for it, sorry.
/ORG

testimento - 25-6-2013 at 03:14

U can flush the system with propane gas if you want, as long as it takes the oxygen out, it will prevent the detonation of aerosols. Indeed I was thinking a system of pot that hold the alcohol where it is distilled and it goes into an insulated pot which is half full of aluminium oxide and under it is strong burner to get the 900c in the pot, and then it would turn into ether and condense into the receiver funnel and flask. If ethylene is produced in minor quantities, i still would consider any yield of over 60% of ether production from ethanol a success compared to the expensive and hard to get sulfuric acid method. if you get ethylene you can vent it off or burn it or use it for other syntheses. I live in a totalitarian state where the sale of chemicals is very highly restricted and state troopers raid people everyday for minor suspicions so i will need to make everything myself, methanol sale is in total ban and even food alcohol cost 70 bucks a liter, luckily they havent banned sugar and yeast yet, haha.

if ether can be made by distilling ethanol over alumina its a god bless for me, removes one major pain in the ass of getting very important solvent.

[Edited on 25-6-2013 by testimento]

starman - 25-6-2013 at 23:07

@ Skeletal clown a couple of notes for you.

A peristaltic pump is superior to an addition funnel.(See my post in Len's thread). It gives you precise adjustable control and can be knocked up from a couple of rollers and tubing for a few bucks.

Be careful of importing glassware. I don't know about Victoria but some states(mine included) have draconian laws in regard to owning glassware.You can get 5 years for possessing a condenser.Be cautious when purchasing anything here.

skeletal-clown - 26-6-2013 at 03:23

@Starman

Thanks for your advice, the peristaltic pump idea seems quite promising, especially if I end up scaling up the procedure.

As for importing glassware, do you mind if I ask where you got that fact about condensers in WA? Before I started ordering glassware I did quite a bit of research on it's legality in Australia and all the information I could find was quite ambiguous.
One of the best sources of information I managed to find was a thread made by another member here: http://www.sciencemadness.org/talk/viewthread.php?tid=14982

By the way, I haven't actually made any ether yet, but I recently ordered a large amount of equipment from Laboy (including a proper addition funnel and a 400mm Graham condenser which I plan to run as a vertical second stage to my 300mm Liebig), for that and other purposes, thanks again everybody for your help.

starman - 26-6-2013 at 22:16

@Skeletal clown regarding glassware restrictions and penalties WA see misuse of drugs act 2004 amendments.There is a thread with the links here somewhere.Queensland is the same or worse,Victoria may be more liberal.
Regarding you setup, I used a horizontal leibig 90deg bend into a Graham vertical,with ice water in the graham and tap water in the leibig,worked a charm.
You'll find it easy to maintain reaction temperature as with the right rate of addition it seems quite self regulating.
Btw I used methylated spirits straight from bunnings and it worked fine.
Apart from using the peri pump and capillary tube and omitting the sand I followed Len to the letter.
Good luck to you in your synthesis.

Found 1 thread
http://www.sciencemadness.org/talk/viewthread.php?tid=12978#pid164842[/url]

[Edited on 27-6-2013 by starman]

skeletal-clown - 26-6-2013 at 23:55

Oh wow, you're right. Queensland and WA seem rather....extreme. How ridiculous! By the way, I found Victoria's act and it seems MUCH less draconian at least as far as glassware is concerned. http://www.austlii.edu.au/au/legis/vic/consol_act/dpacsa1981... or more specifically www.austlii.edu.au/au/legis/vic/consol_act/dpacsa1981422/s80...
Thanks for your advice though, I'm glad I'm in Victoria!

As for your apparatus, that sounds near identical to mine!

starman - 27-6-2013 at 22:57

Yeah lucky you. It seems in Victoria there is no law against possessing chemistry equipment whatsoever.(as there fucking well shouldn't be anywhere!)
The Victorian act seems to only call for EUD record keeping of suppliers.
As for me,I am in the unenviable situation of possessing a fairly well set up amateur lab and having to conduct everything on the down-low like I'm some sort of criminal.
Maybe one day in this country we'll have something like a bill of rights to protect individual freedom on a national basis.

skeletal-clown - 28-6-2013 at 21:38

I hope so, the current legislation in most of the country is ridiculous!! These laws are simply blatant anti-intellectualism.

RobertRobinson75 - 29-6-2013 at 01:58

Quote: Originally posted by skeletal-clown

I hope so, the current legislation in most of the country is ridiculous!! These laws are simply blatant anti-intellectualism.

I agree with this completely. As someone who is trying to teach themself and get into doing chemistry at home, it's very off-putting. I can't get a condenser or still head where I live as well, which is very frustrating.

Oscilllator - 29-6-2013 at 02:04

sciencesupply has an absolutely terrific chart for glassware for all states. here's the link:
http://sciencesupply.com.au/shop/content/2-legal-notice

skeletal-clown - 29-6-2013 at 21:04

Thanks, that chart puts it all in a nicely set out form. I'd just like to mention however, that at least for Victoria the items in red are classified as "category 3 precursor apparatus". This DOESN'T mean they are illegal, it just means that you have to either have an account with the company you buy them from, or you have to sign an end user declaration. ( Drugs, Poisons and Controlled Substances Act 1981, page 180 and Drugs, Poisons and Controlled Substances (Precursor Supply) Regulations 2010, page 9).
So long story short, in Victoria at least you can still own these items, you just have to jump through a few hoops.

starman - 30-6-2013 at 00:19

My problem was I had the full established lab prior to 2004 (when the WA government enacted legislation making the possession of glassware illegal)
Even if I was prepared to give up amateur chemistry (not for nobody) what does the WA gov expect.That I'll throw thousands of dollars of glass and gear in the garbage?
On the bright side for everybody else but WA and QLD it seems you can import all the equipment you want.No need for registered accounts or EUDs.Nobody's business and no laws broken.
Sorry,I've taken us a long way off topic,but these things need to be bitched about.

testimento - 30-6-2013 at 03:56

What if you consider making the needed ware yourself? I can do most processes fine with my stainless steel self made ware. Labware isnt illegal in here, but there are no suppliers because nobody buys them.

skeletal-clown - 1-7-2013 at 05:44

@starman, I couldn't agree more, bitching is good!

@testimento, That is well beyond the reach of many amateurs (myself included), but could be a great way to obtain glassware in such places. I think there's even a book on it in the SM library...

xfusion44 - 27-5-2015 at 18:44

Hi, could HCl be used instead of H2SO4? I've read on wiki that you need strong acid and that H2SO4 is usually used, but it doesn't say what other acids can be used. Thanks in advance!

BR, xfusion

Magpie - 27-5-2015 at 20:01

I don't think so. The big advantage of H2SO4 is that it is a non-volatile acid. HCl is a very volatile acid. Quoting from Len1's procedure in Prepublication:

"The main requirement is that the combined initial reagent water should not make the initial H2SO4 concentration less than about 70%, at which point the boiling point of the mixed acid approaches the reaction temperature used in step 2 - and it will start distilling over with the products."

byko3y - 27-5-2015 at 20:15

HCl is volative, as well as chloroethane (b.p.12.3°C vs 33°C for diethyl ether).

macckone - 28-5-2015 at 01:33

The volatility really has nothing to do with it.
Sulfuric acid is a dehydrating agent.
Obviously Hydrochloric acid contains a LARGE amount of water.
Quite the opposite of what you want.
In theory other acidic dehydrating agents like phosphorous pentoxide could be used. But sulfuric acid is actually easier to handle than that one. Alumina can also be used as dehydrating agent at high temperatures. A better choice for this particular reaction is anhydrous sodium bisulfate. It has less by products and is more readily available.

DJF90 - 28-5-2015 at 02:32

Quote: Originally posted by macckone

A better choice for this particular reaction is anhydrous sodium bisulfate. It has less by products and is more readily available.

Are you speaking from experience or do you have a reference for that claim? Please provide further details.

xfusion44 - 28-5-2015 at 03:21

So, is the H2SO4 used because of its acidity or high dehydrating ability or both?

So, I could use solid acids, with dehydrating ability?

byko3y - 28-5-2015 at 05:58

macckone, thionyl chloride dehydrates and contains acid, but EtOH + SOCl2 does nothing except of EtCl, and on dehydration you get ethylene, which actually is an unwanted side-product even in the EtOH-H2SO4 method.
Nice idea about phosphoric acid, hovewer I don't know about its selectivity towards etherification and dehydration.

I know that ethyl sulfuric acid (EtSO4H) is an intermediate in the ether synthesis, but I have no idea about the mechanism (this one is probably wrong https://commons.wikimedia.org/wiki/File:Acidic-ether-synthes... )
macckone, have you or somebody else ever succeeded in making ether using sodium bisulfate? I hear about it first time.
xfusion44, all known routes require some dehydration power (until you use already dehydrated precursors). As you might know, alumina (Al2O3) is a close equivalent of sulfuric acid, but in the gas phase heterogenous reaction; they both are acidic and convert alcohols to olefin or ether, depending on conditions.

[Edited on 29-5-2015 by byko3y]

xfusion44 - 28-5-2015 at 06:13

@byko3y

So, it should work with alumina?

Thanks!

byko3y - 28-5-2015 at 21:11

xfusion44, Diethyl ether synthesis on alumina is a well studied method. There are reports in the web on extensive researches of the process for different catalysts and conditions, also, Ullman briefly describes the commonly used industial process (with usual alumina).

byko3y - 29-5-2015 at 04:32

https://web.anl.gov/PCS/acsfuel/preprint%20archive/Files/49_...
Here's the paper in case you failed to find one. I want to emphasize that you can't obtain more than 60% ether per pass and the maximum conversion is 70%, but high conversion leads to higher amount o by-products, so the highest seelctivity on aluminophosphate catalyst requires implies conersion as low as 50% per pass.
Sulfuric acid method gives perfect yield and selectivity when done properly.
An interesting result of the research: you actually need a lewis acid to synthesize the ether. Ethylsulfuric acid plays its role in case of sulfuric acid method. I think sodium ethyl sulfate will work too, but it needs to be pre-formed, otherwise this stuff will hydrolize right away.
I did not find any paper that could describe ether synthesis via phosphoric acid even remotely. Phosphate esters are relatively stable and phosphoric acid is a weak acid. Phosphoric acid on silica can lead to diethyl ether, but I think that on higher conversion rates it will just dehydrate it to ethylene (phosphate is a bad leaving group).
Ionic resin is capable of promoting the etherification with excellent selectivity, but it either requires some drastic conditions http://qap2.onlinelibrary.wiley.com/doi/10.1002/aic.14497/ab... or is not usable because of polimerisation at higher temperatures.

macckone - 2-6-2015 at 09:13

Quote: Originally posted by DJF90

Quote: Originally posted by macckone

A better choice for this particular reaction is anhydrous sodium bisulfate. It has less by products and is more readily available.

Are you speaking from experience or do you have a reference for that claim? Please provide further details.

Mellor inorganic chemistry is where I first read about it and experience. It produces less sludge. And it is available at most wally world stores.

macckone - 2-6-2015 at 09:24

Quote: Originally posted by byko3y

https://web.anl.gov/PCS/acsfuel/preprint%20archive/Files/49_...
Here's the paper in case you failed to find one. I want to emphasize that you can't obtain more than 60% ether per pass and the maximum conversion is 70%, but high conversion leads to higher amount o by-products, so the highest seelctivity on aluminophosphate catalyst requires implies conersion as low as 50% per pass.
Sulfuric acid method gives perfect yield and selectivity when done properly.
An interesting result of the research: you actually need a lewis acid to synthesize the ether. Ethylsulfuric acid plays its role in case of sulfuric acid method. I think sodium ethyl sulfate will work too, but it needs to be pre-formed, otherwise this stuff will hydrolize right away.
I did not find any paper that could describe ether synthesis via phosphoric acid even remotely. Phosphate esters are relatively stable and phosphoric acid is a weak acid. Phosphoric acid on silica can lead to diethyl ether, but I think that on higher conversion rates it will just dehydrate it to ethylene (phosphate is a bad leaving group).
Ionic resin is capable of promoting the etherification with excellent selectivity, but it either requires some drastic conditions http://qap2.onlinelibrary.wiley.com/doi/10.1002/aic.14497/ab... or is not usable because of polimerisation at higher temperatures.

You could be right on the phosphoric acid. I was speaking theoretically.
not sure who you were responding to in your other post but I am not advocating thionyl chloride.

byko3y - 13-3-2017 at 03:26

I really want ot correct myself about ethanol-sulfuric acid route being much better than catalytic one. Considering all the information I've gathered recently, for sulfuric acid route conversion is somewhere at 35-50% per pass, 90-95% of it being diethyl ether when done correctly. That's pretty much the same numbers as for alumophosphate catalyst on low conversion mode (which is preferential due to higher selectivity). There must be some kind of equilibrium Et2O + H2O <-> EtOH + Et-Cat which does not allow ether yield to go past the 50% mark, no matter it is heterogenous or homogenous reaction.
And here's the main thread with sulfuric acid-ethanol discussion and practice: http://www.sciencemadness.org/talk/viewthread.php?tid=9747

[Edited on 13-3-2017 by byko3y]

JJay - 13-3-2017 at 07:55

I've made ether with sulfuric acid a few times. It does produce some disgusting sludges with denatured alcohol but hardly even turns pink with pure ethanol.

clearly_not_atara - 10-6-2017 at 21:32

Okay, so I just thought of a dumb idea. Someone explain to me why it won't work.

Potassium pyrosulfate + potassium ethoxide (refluxing ethanol?) >> potassium ethyl sulfate + potassium sulfate
Potassium ethyl sulfate + potassium ethoxide >> diethyl ether (g) + potassium sulfate
K2S2O7

Basically ethoxide attacks pyrosulfate as a nucleophile. I wrote potassium but maybe lithium or some other counterion would be better idfk. Potassium pyrosulfate is probably not all that soluble in ethanol but i think it would be more soluble than sulfate because disulfurjc acid is a much stronger acid and salts of superacids are usually pretty soluble

JJay - 10-6-2017 at 21:57

I think water would be extremely detrimental to the yield. I'm also not sure if it would be possible to carry out the second reaction at a reasonable rate below the boiling point of ethanol.

byko3y - 11-6-2017 at 19:55

I like the idea, but the reaction requires temperature above 100 C (just as a classic reaction does) while alcohol boils at atm. pressure long before the temperature is reached. Classical synthesis solves the problem via ethylsulfuric acid formation, which is non-volatile but is slowly hydrolyzed.
Working without solvent at 250 C might work, however I have no idea about stability of reagents and intermediates.
Also, synthesis requires not so easily accessible reagents, so I doubt anyone would try it. It might be easier to do a straightforward EtI + NaOEt, which gives no nasty byproducts.

JJay - 11-6-2017 at 22:01

You can actually make ether at 70 C, but it's very slow. There's a huge increase in the reaction rate right around 130 C; I think this is due to Gibbs free energy crossing a threshold permitting a secondary reaction mechanism, but I'm not exactly sure what.

[Edited on 12-6-2017 by JJay]

clearly_not_atara - 12-6-2017 at 15:39

I was looking for solvents that should be compatible with the reactants and OTC. My best idea so far is mononitrotoluene bp 210 C. I'm not sure if this is compatible with ethoxide? I'm guessing some of the nitrotoluene will be deprotonated particularly any 2-nitrotoluene (since a mixture of nitrotoluenes is easiest to make), but not most (ethanol is a stronger acid), and the nitrobenzylsulfonate salt should be inert (to rxn conditions), I hope? I could see this byproduct causing problems if the mixture is acidified but diethyl ether should distill out and then maybe you recover the solvent by reduced-pressure distillation?

If I had to guess lithium is the best counterion because of its Lewis acidity.

Other possible OTC solvents for ethoxide include menthol and methylsulfonylmethane.

[Edited on 12-6-2017 by clearly_not_atara]

Fyndium - 15-2-2021 at 00:05

Why alumina catalyzed dehydration is not discussed anymore in here? It sounds like a perfect solution for ether generation.

I have some alumina powder purchased from a pottery store. Could it possibly have catalytic properties as is? It's not grit, it's just a very fine white powder as-is.

https://doi.org/10.1007/s10934-018-0663-7

This paper describes that an alumina catalyst at 200-300C will produce mostly ether, with some ethylene formed. The yields vary between 20 to 50 percent, lower being for zero ethylene, and upper being for 10%. So, for every liter of input ethanol, 200-500mL of ether should be obtained, and 0 to 100 grams of ethylene gas. These are very crude numbers, for the record.

I suppose a tabletop generator could be manufactured by submersing a 500mL rbf into a metal shot bath filled halfway with alumina, and a gas washer where ethanol vapor would be led in, and the exhaust gas would be led through a graham condenser into a collection flask, and exhaust tube with another condenser would be vented away for ethylene gas.

Graham should be cooled with cold water, as it will condense everything at first and a lot of energy will be transferred into it, so the water needs to be replaced often or recharged with ice, I noted this just as I stripped a batch of ethanol clean and the coolant water heated up very quickly.

The collecting flask and the exhaust condenser should be cooled with salt-ice water separately, as their purpose is to keep the condensate cold and prevent vapors escaping. If one's got the glassware and interest, one could actually make a double trap to condense the ethanol first at 40C and cool the second receiver to concentrate the formed ether, requiring less work afterwards. Continuously operating plant would warrant using dropper funnels to drain the receivers for reuse without stopping and dismantling the whole apparatus, and might be worth considering given the setup is arduous enough to get up so making only few hundred mL of ether would be extremely un-rewarding. Given the droppers are more expensive and difficult to cool with a bath because of their structure, simply draining the flasks with silicon stoppers in one of the joints and glass tubes and a primer pump could be an option.

For 200C silicone oil would work, but for 250C we're getting too high and it likely smokes like a BBQ, so a metal shot bath would probably be a better choice. Metal also conducts heat so well that it would work, as sand or salt are much better at insulating than transferring heat. Metal shots could be replaced with smallest nuts (M4, M5 otc) as they're sold 5€ a kg in bulk and are generally available everywhere. They are zinc coated, so it might be worth considering either pickling them first or heating them to high heat to burn it off. Prior flushing with any inert gas (CO2, argon, N2) would render it safe for DEE autoignition temp of 160C. The large thermal mass also makes temp control easy and fluctuations smaller to both directions.

[Edited on 15-2-2021 by Fyndium]

macckone - 16-2-2021 at 14:56

The high temperature catalytic route is usually not discussed because it is harder for the average person to do.
sulfuric acid or sodium bisulfate are easier for most people to get prior to the sulfuric acid crackdown in the EU.
I am guessing sodium bisulfate is still unregulated and does a good job.
In my opinion it is better than sulfuric acid. Sulfuric acid is formed in situ and reacts with the ethanol.
Less ethylene is formed to polymerize.

The usual method of doing a gas phase reaction is a silica or alumina tube, with the center heated with direct flame or nichrome wire.
With the tube method you can feed the ethanol in one end and extract the ether at the other.

However you need to periodically purge the system of water.
This is true regardless of the method used as the reaction is reversible at high temperatures.

Fyndium - 16-2-2021 at 21:41

Apparently sodium bisulfate would be the most otc straightforward method for ether if it works as depicted. It will produce ethyl sulfate at lower temperatures, and question is if the generation is equimolar or catalytic, as if it was molar conversion, it would require hefty amounts of bisulfate to produce ether.

Doesn't water come over with ethanol/ether/ethylene as vapor and condense to the receiver flask?

The tube method is apparently the classic, but my concern is that too high temp will produce more other products than desired, as the research paper indicates that much above 300C the main product by far will be ethylene. Hence my idea was to use metal/sand bath immersed flask trap with the catalyst to control the temperature. Flame heated tube temperature range can be anywhere between 200C and 900C, and temp control is difficult, along with hotspots.

Gotta test it out, as they say.