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Author: Subject: 1,4-Dioxane from Ethylene Glycol and H2SO4
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[*] posted on 17-11-2022 at 01:02


May i suggest testing/purifying your H2SO4
Lots of videos out there about this subject. Your initial distillate should smell sweet, don't go sniff it. It's a powerful smell that will fill an outside area if it's not too windy




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[*] posted on 17-11-2022 at 14:54


I have about 500ml of distilled H₂SO₄ left and a couple liters of liquid fire drain cleaner. I am hoping to stretch the distilled until another warm spell hits, as I would prefer to do it outdoors away from all my machine tools and it is looking like cold and snow for … who knows?
I originally did this with the distilled with the same results, even though I used NaOH at the time. I did grab some Prestone concentrated while in town today. I’m going to try it here tonight and see which way it goes. I really want to get all the glassware cleaned up because it smells. Yes there is some sweet smell in the last flask, but the yield is very minimal.
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[*] posted on 23-2-2023 at 20:58


Just tried out my own attempt at dioxane, and I got what I wanted, although it was stopped not by prudent choice but by me yeeting the receiver before a sludge volcano came over (luckily all contained in glassware).

How are people dealing with the waste from this, given throwing dioxane down the drain is not the best of ideas? Is absorbing it into something, sealing in bags, and using the trash acceptable?

Was on my mind since I'll have more clean-up than expected...
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[*] posted on 23-2-2023 at 21:38


alexrandomkat - no tar, no volcano: https://www.sciencemadness.org/whisper/viewthread.php?tid=65...
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[*] posted on 23-2-2023 at 21:48


Thanks, should have read that thread before I started...

Just stopping a tad earlier would have saved me a lot of hassle now.
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[*] posted on 24-2-2023 at 04:36


Use less acid and bigger flask or put smaller volume into your flask. You can repeatedly add fresh ethylene glycol and resume synthesis. I used 1 L flask and filled 300 ml into it, distilled out 200 ml so remainder in flask 100 ml... then added fresh 200 ml of glycol and repeated (4 cycles totally). Finally I distilled the content from flask a little more so only 50 ml remained inside (from that 11 ml should be H2SO4). Could be done using dropping funnel instead adding glycol on cycles. When I saw the disastrous situations on youtube I postponed this synthesis for more than 1 year. Meanwhile I luckily found better sources like using 3 times less of catalyst and bigger flask filled less. I wonder whether H3PO4 could be used instead of H2SO4 but I usually do not repeat experiments as I have long list of new experiments to do. Meanwhile I also bought a lot of 1,4-dioxane from es-drei.de
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[*] posted on 5-3-2023 at 16:13


Interesting update. I finally got around to cleaning up all the different fractions I collected from both the ethylene glycol distill and dioxane. There was perhaps 30-40mL total. I put them all in a gallon jug (empty distilled water). All those test tubes were capped, since I really don’t care for the smell of it.
There was one last tube in that rack, unmarked and open with a mL or so of a clear liquid. It couldn’t be to volatile, and being from the same time I just put it in the same jug.
A few seconds later, all the vapors ignited in a single woof. I felt the jug, but no heat was noticed.
I wish I knew what was in the open tube, and why it reacted the way it did.
Also regret assuming it was fine to just throw in with the dioxane/EG/ mystery yellow liquid.
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[*] posted on 5-3-2023 at 17:30


If this stuff has been sitting, waiting for 3 months, it likely formed peroxides



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[*] posted on 16-7-2023 at 01:42


After that 350 g of the product stayed in 0,5 l bottle for almost 1 year in a fridge at +4C, in the bottom part of the flask a solid block of product was formed and the liquid moved above. This happened due to higher density of solid 1,4-dioxane and lower density of liquid phase (this also ensures the flask does not break unlike water expanding during freezing) and hundreds (or maybe almost thousand) of partial thaw / resolidification cycles by small temperature oscillations in the fridge.
I poured the top liquid phase (which volume increased from 20 ml into 100 ml during 1 year) into another flask and let magnetically stirred with 2 g of 90% KOH for 1 day. Most of KOH dissolved but still some solid KOH remained. There was a reaction very likely aldol condensation (remaining of acetaldehyde ???) because the content turned into yellow and after few hours into brownish. After turning off the stirring a dark brown mess settled to the bottom and the upper phase was filtered through filter paper into new clean flask using gravity filtration. 1 g of calcium metal (small 5 granules forged with hammer into thin pieces to expose fresh surface) was added to the yellowish filtrate and there was very slow and tiny bubbling of H2. I let it to magnetically stir for 1 day and then redistill.
The 250 g of solid dioxane block was let to melt at room temperature and then magnetically stirred with 2 g of KOH, but this was very likely unnecessary, this solid phase seems to be very pure (and no liquid seems to be trapped among crystals inside the solid block): there was no reaction with KOH and it stayed completely clear and colorless, pellets of KOH seems to be still dry and not covered with a layer of liquid. I later added 0,25 g of calcium metal forged with hammer into thin pieces with exposed fresh metal surface and there was no reaction either. So this phase seems to be very pure and also anhydrous. I'll redistill it too. There is no need to add KOH either drying agent (Ca or Na) into this phase, either redistillation. Just let you know what I tried and what seems to be unnecessary.
Letting the product to sit in a fridge for 1 year seems to be enough for the purification. Initially the upper liquid phase was circa 20 ml, but during time the trapped liquid moved from the bottom solid phase to the top liquid phase and it was easy to separate it by just simply pouring it out. It is also a good idea to let the solid dioxane in the fridge until its usage for e.g. as a solvent for a Grignard reaction. In its solid form at +4 C fridge temperature it is pure, anhydrous, no risk of peroxide formation.
Patience is our biggest helper.

[Edited on 16-7-2023 by Fery]
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[*] posted on 7-9-2023 at 20:59


I am in need of some 1,4-dioxane for an an experiment that I intend to do once I have sourced the required regents and solvents. I intend to make the 1,4-dioxane via dehydration of ethylene glycol with sulfuric acid. I recently purchased some impure ethylene glycol (anti freeze) for this purpose. What I have unfortunately realised since purchasing the ethylene glycol is that it is 50% water.
Is it worth distilling the ethylene glycol to remove the water before I attempt the dehydration reaction with sulfuric acid?
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[*] posted on 7-9-2023 at 21:04


I would.

That said, I have never been very successful at dioxane synthesis. I have used ~100% ethylene glycol and also the same stuff pre-distilled. I think I have lost a lot in the work-up with NaOH or KOH and made a lot of tarry goop. Which is to say, my advice might not count for a whole lot.
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[*] posted on 7-9-2023 at 21:44


Thanks, I have never tried the synthesis, so any advice is most welcome. I was concerned my crude product would be too dilute and the dioxane I produced would get mostly lost when I was trying to pull the water out. I will get rid of the water first.
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[*] posted on 8-9-2023 at 05:04


Certainly remove the water as much as you can. During the reaction use only less of the catalyst, not 10%. 4% was enough in my case. You can add fresh ethylene glycol then and repeat few cycles. Do not overfill the flask. Filling for only 1/3 is better than filling 1/2 of the flask.
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[*] posted on 27-11-2023 at 13:11
Runaway polymerization during dioxane synthesis?


While making dioxane yesterday for the first time, I noticed something strange. I was using unpurified antifreeze (300 mL) and purified drain cleaner acid. The distillation went pretty smoothly for the first two hours, with none of the tar people talk about. It did slowly grow darker until it was almost black, but there was no foaming. The vapor temperature had been fairly stable at around 110*C, but when around 100 mL was left in the boiling flask the temperature suddenly spiked. It climbed to over 120*C and a lot of distillate came over very rapidly, maxing out my condenser. Even though I immediately turned off the heat it continued to keep going. About 50 mL came over in just a few minutes. Tar also started to form, and foamed up almost to the condenser.

Could the rapid polymerization reaction cause the heating? The exothermic reaction that forms Bakelite comes to mind. Usually, it seems the tar forms over a couple minutes. Mine, however, formed all at once. I did add a little less sulfuric acid than most people(30 mL).

IMG_0093.jpeg - 3.1MB
End result.

[Edited on 11-27-2023 by Sir_Gawain]




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[*] posted on 28-11-2023 at 01:15


what was your ratio of ethylene glycol : H2SO4
volume of your flask and volume of reactants?
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[*] posted on 28-11-2023 at 06:56


300 mL antifreeze, 30 mL sulfuric acid, 500 mL flask.



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[*] posted on 28-11-2023 at 08:05


Oof. I don’t envy the task you have ahead of you with cleaning that flask.

I can’t explain what happened, but I recommend carefully re-distilling your product, because who knows what all came over when the temperature spiked.




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[*] posted on 28-11-2023 at 08:50


Quote: Originally posted by Texium  
Oof. I don’t envy the task you have ahead of you with cleaning that flask.

It actually wasn’t that bad. Hot water got most of it out, a little acetone removed the rest.
I’m going to fractionally distill it, dry over sodium hydroxide, and distill again.




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[*] posted on 28-11-2023 at 11:11


Quote: Originally posted by Sir_Gawain  
300 mL antifreeze, 30 mL sulfuric acid, 500 mL flask.

for 300 ml glycol you should use 1 L flask and 11 ml of H2SO4
distill out 200 ml of product and then add fresh 200 ml of glykol into the flask and repeat few times
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[*] posted on 28-11-2023 at 12:29


Only 11 mL of sulfuric acid for 400+ mL of glycol? I reasoned less sulfuric acid would cause less tar, but that seems like a lot less.



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[*] posted on 28-11-2023 at 18:41


Likely you made some polyethylene glycol in the process, that might happen if mostly glycol and not enough acid. The acid might help stop the polymerization and make dioxane rather than chain elongation.
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[*] posted on 28-11-2023 at 21:40


Everyone repeats the mistakes of former home lab experimenters although everyone sees the consequences. I postponed this synthesis for few years only due these nasty looking experiences - black tar and messing apparatus with it. If at least one had did the experiment properly I did it few years earlier.
Here the method to avoid nasty experiences:
https://www.sciencemadness.org/whisper/viewthread.php?tid=65...
Use 1/3 of the H2SO4 amount the unhappy experimenters used and use twofold volume flask compared to them. Distill off only 2/3 of the content from the flask. Then you can add the consumed glycol amount and resume. You can perform few such cycles.
https://www.sciencemadness.org/whisper/viewthread.php?tid=15...
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[*] posted on 29-11-2023 at 05:00


It's been a few years since I've made any but I remember having to carefully control the power output on my heating mantle. Toward the end of the distillation it will go crazy and foam out of control, so you have to babysit it and taper down the power and play with the stirring speed, and there will be a point where you have to call it quits. You can push the distillation pretty far, however.

I used a 1L round bottom flask + 350 ml ethylene glycol (distilled from antifreeze concentrate) + 35 ml unbuffered drain cleaner straight from the bottle (tested as 93% w/w concentration.) http://www.sciencemadness.org/talk/viewthread.php?tid=84819&...

[Edited on 11-29-2023 by monolithic]
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[*] posted on 29-11-2023 at 09:11


Here you go: the dioxane sticky thread that people have been wanting for years but was never made!

[Edited on 11-29-2023 by Texium]




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[*] posted on 2-12-2023 at 12:54


Thanks, Texium!

Fery, I’ll try your method next time.

Another improvement I discovered is, when drying the impure dioxane azeotrope over sodium hydroxide, to add about 30 grams of sodium hydroxide per 150 mL of dioxane and let it dissolve. At this point, Nurdrage added more sodium hydroxide and it all gummed up and solidified. Instead, drain off the bottom aqueous sodium hydroxide layer and add another 30 grams of sodium hydroxide to the dioxane. You lose a lot less dioxane this way. It’s also probably drier.




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