Sciencemadness Discussion Board

1,4-Dioxane from Ethylene Glycol and H2SO4

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Fery - 3-12-2023 at 09:52

Hi Sir_Gawain, maybe the best route would be a continuous method like filling 500 ml RBF with 100 ml of ethylene glycol + 10 ml of conc. H2SO4, heat and when the dioxane starts to distill, then drip new fresh glycol into the RBF from a dropping funnel at a similar drop rate as observed from the condenser. But the funnel could be unavailable or too expensive for someone, in that case just use 1 L RBF + 300 ml glycol + 10 ml H2SO4. Distill out 200 ml, then slightly cool RBF (like 100 C) and add fresh 200 ml of glycol. Repeat. I did 4 such cycles. The last time do not distill too far (the last cycle I let 50 ml in the RBF and no tar, no runaway into condenser, easy to pour out the remainder from the flask and washing it with water and the flask still looks like a new one). Refilling RBF and repeating few cycles should be a method available for everyone. I won't repeat this experiment. I usually do everything only once. I have a big to-do list.

[Edited on 3-12-2023 by Fery]

Sir_Gawain - 3-12-2023 at 16:15

Quote: Originally posted by Fery  
Hi Sir_Gawain, maybe the best route would be a continuous method like filling 500 ml RBF with 100 ml of ethylene glycol + 10 ml of conc. H2SO4, heat and when the dioxane starts to distill, then drip new fresh glycol into the RBF from a dropping funnel at a similar drop rate as observed from the condenser.
[Edited on 3-12-2023 by Fery]

Like making diethyl ether. I have recently acquired an addition funnel, so I think I’ll try it.

Sir_Gawain - 3-12-2023 at 18:20

Would it help to use a vigreux column with this method? For the first distillation.

Fery - 3-12-2023 at 21:58

Do you mean the column attached to the reaction flask or do you mean the first distillation of the already obtained dioxane?
Using Vigreux column attached to the reaction flask seems not to have any significant advantage. You just need to distill out water and dioxane as they are formed. B.p. of ethylene glycol at atm. pressure is much higher. I do not know the temperature of the reaction but if it is similar to diethylether synthesis (cca 140 C) then at such temperature only very small amount of ethylene glycol distills out (its b.p. 197 C so at 140 C its partial vapor pressure is still quite low). Using an uninsulated column may slightly precool the vapor so it enters the condenser with a little lower temperature. The vapor has very likely the same temperature as the temperature of the reaction inside the distillation flask and nothing condenses at the column when such overheated vapor passes the column. Only when you later process the distillate it will distill at the temperature of its own b.p. When synthesizing diethylether it seems to be good idea to return unreacted ethanol back into the reaction / distillation flask as its b.p. is lower than the temperature of the reaction so significant amounts of ethanol are carried out from the reaction flask by the vapor - here I would very likely try 2 condenser system where the first condenser will be like reflux condenser with circulating water of a temperature slightly above b.p. of diethylether to condense unreacted ethanol and then second downward condenser with ice cold water circulation and preferably powerful type (like spiral) for condensing the diethylether.

[Edited on 4-12-2023 by Fery]

Fery - 4-12-2023 at 06:12

I did purity checks of the product by freezing it for half a year in fridge at +4 C, small oscillations of the temperature helped to make a solid mass of crystals in block at the bottom and a liquid phase above from initial mix of crystals with trapped liquid. I tried to dry the liquid phase with Ca metal for half a year and it seems the cause of the liquid was not water, because only minimal amount of H2 released + only few tiny bubbles of H2 observed and the further "dried" liquid gave only few small crystals when returning back into the fridge. What helped was today night when I put it outside into -15 C which gave about 50 g of crystalline dioxane which I sucked well on sintered glass using hand vacuum pump still outside in the frost. And 50 ml of liquid which is still certainly rich on dioxane but contaminated with something which prevents its solidification. It could be only a little of something like 5-10% of contaminant. It seems not to be water. Could be very likely aldol condensation product of the sideproduct acetaldehyde, but-2-en-al (crotonaldehyde). It's b.p. is 102 C which is quite close to dioxane and impossible to separate using simple distillation (would require powerful column and variable ratio distillation head if it does not form and azeotrope with dioxane at all).
So to test the purity I suggest these freezing experiments after drying with alkaline metal to be sure the contaminant is not water. And let the small oscillations of the temperature around +4 C to make the work for half a year (every cycle the higher density crystals go downwards and the trapped liquid among crystals with lower density migrates a little bit upwards so at the end it is easy to simply pour out all the liquid). If you freeze for only one day then the separation of crystals from liquid requires vacuum filtering on very cold air but not for too long as it introduces air moisture into the product.

Sir_Gawain - 4-12-2023 at 06:59

Quote: Originally posted by Fery  
Do you mean the column attached to the reaction flask or do you mean the first distillation of the already obtained dioxane?

I meant the first distillation from the reaction mixture. Besides pre cooling the vapor it could also provide extra space for a foam over.

XeonTheMGPony - 25-12-2023 at 05:35

Well I have an over head stirrer now, so I got all the parts, I guess I better clean the lab up and set up a synth via the Iron sulfate method set up.

Farming been eating up lot of my time as of late so no time line! But excited to set up and share!

Chemateur80 - 26-2-2024 at 09:23

I had an interesting experience some years ago when distilling 1,4-dioxane from Na-Mg-aggregate to dry it, and possibly isolate som sodium metal.

The distillation went smoothly until the end, when the temp started rising quite rapidly. I quickly turned off heat and switched out the receiving flask for a new one, and then the fun started.
At first there was a white mist and then the contents of the boiling flask lit up and burned with a nice bright yellow flame.
Guess I had gotten some sodium...
I backed away quickly and hoped for the best. Fire extinguisher ready.

The burning sodium was kinda beautiful to watch. A bit nerve-racking too.
However, the fire went out after maybe 20-30 sec.
I couldn't see any damage done to the RBF. I suppose the sodium just burned on top of the MgO-layer.

I guess distiling to (near) dryness is a bad idea. Air must have been sucked into the system when I switched out the receiving flask and lowered the temperature in the boiling flask, and then the molten sodium caught on fire.
Has anyone else experienced this?

I haven't used my dioxane for a few years now. It's been stored over sodium metal and NaOH. Guess I need to test it for peroxides.
Should I be worried?

Making dioxane was a mess, with low yields, so I really need to try the method by Fery, where fresh EG is added in portions or continuosly.

Sir_Gawain - 26-2-2024 at 10:05

I was distilling dioxane over sodium metal once and it distilled to dryness (I should have watched it more closely). The sodium completely burned up the ptfe stir bar and filled the still with carbon. The rbf was badly etched, but thankfully the dioxane that had distilled over didn't catch on fire. I'm thinking that the molten sodium ripped the fluorine from the ptfe, leaving carbon.

Chemateur80 - 27-2-2024 at 14:50

Quote: Originally posted by Sir_Gawain  
I was distilling dioxane over sodium metal once and it distilled to dryness (I should have watched it more closely). The sodium completely burned up the ptfe stir bar and filled the still with carbon. The rbf was badly etched, but thankfully the dioxane that had distilled over didn't catch on fire. I'm thinking that the molten sodium ripped the fluorine from the ptfe, leaving carbon.

Ouch.
Yup, I really should have kept a closer eye on my distillation as well.
No destroyed stirbar in my case. The Na-Mg-mix was too thick to stir.
Never distill to dryness, as they say. Guess they were right about that.

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