Warning: Sulfuric acid and potassium hydroxides are corrosive, wear gloves when handling them.
Dimethyl dioxane is not sufficiently characterized in terms of health hazards.
Although I would assume it's likely carcinogenic due to its similarity to dioxane.
Best to err on the side of caution.
Greetings fellow nerds.
In a previous video i made dioxane from ethylene glycol found in domestically available automotive antifreeze.
Interestingly enough there is another type of glycol, propylene glycol, that's also available as antifreeze as well as a solvent for electronic cigarette liquids.
We can actually make dimethyl dioxane from this.
So we're going to do that in this video.
I'll let you know up front though there doesn't seem to be any special use for it so i'm just producing this video for didactic value.
Anyway, first we need our source of propylene glycol.
I'm going to be using this waterline antifreeze meant for RVs.
Make sure it says somewhere on the label that it's made with propylene glycol.
You can also use pure propylene glycol from electronic cigarette liquid if that's available to you.
Now we need to purify our propylene glycol.
So we setup a simple distillation apparatus.
I'm going to put on this foil shroud to keep the heat in.
Now we just turn on the heating and start distilling.
My antifreeze was premixed with water so that's going to distill off first.
The distillate temperature is a bit higher than the boiling point of water because i'm cranking the heat up to speed up distillation.
Keep distilling until the distillate temperature crosses 150 celsius and start collecting.
Propylene glycol actually has a boiling point of 188 celsius and if you desire highly pure propylene glycol you can wait until that temperature is reached.
I'm not bothering since a tiny bit of water contamination will be inconsequential for my purposes.
Now you might be wondering why i'm going through this trouble of distillation.
I actually tried producing dimethyl dioxane straight from antifreeze but the yield was terrible and there was a large amount of tar formation.
Additives in the propylene glycol antifreeze presumably interfered with the synthesis.
You can actually see these additives break down and precipitate out now as this white powder.
Most dramatic is the red dye used to color the antifreeze is also breaking down.
If you're using pure propylene glycol straight from electronic cigarette suppliers then you can skip the distillation and go straight to making dimethyl dioxane.
Anyway we distill until dry.
And there is our propylene glycol, purified and ready for use.
Over here in the boiling flask is the residue of additives.
As you can see this is a lot of stuff and was certainly a contributing factor to my earlier failures.
Anyway, to make our dimethyl dioxane we get 800 mL of our propylene glycol and add to it 50mL of concentrated sulfuric acid.
I'm using low grade drain cleaner acid.
Then we simply set up for distillation and slowly turn up the heating until the reaction starts and we start distilling.
Adjust temperature for a distillate drop rate of about one drop every 2-3 seconds.
So what's happening? The sulfuric acid catalyses the condensation of two propylene glycol molecules to make dimethyl dioxane and water.
You actually get a mixture of products depending on how the propylene glycol is oriented.
But they're both technically dimethyl dioxane.
Anyway, I kept distilling until the distillate changed from a light yellow to a significant yellow.
Possibly indicating a change in products as the tar build up dominates.
And here is all my collected product, dimethyl dioxane and water.
Interestingly, dimethyl dioxane isn't miscible with water like regular dioxane is.
So it separates into two layers like this with water on the bottom.
Now with regular dioxane to destroy impurities you add in sulfuric acid.
But i found out the hard way the dimethyl dioxane is highly susceptible to acid catalyzed hydrolysis so destroying impurities this way is not a good idea.
You actually end up destroying the dimethyl dioxane as well.
Instead impurity destruction with a strong base should be used.
First use a separatory funnel and separate out the lower water layer.
This is to remove most of the unnecessary volume and make this easier to work with.
You might be wondering why i have so much more product in this shot,
it's because i had to rerun my reaction from an earlier failure of the acid catalyzed hydrolysis.
Anyway, at this point you can use a dean stark trap to remove all the remaining water but this is optional.
Add in about 40g of potassium hydroxide and stir.
A lot of impurities like ketones, aldehydes, leftover propylene glycols and so on will react with the potassium hydroxide and form less volatile products.
This will allow us to distill off the dimethyl dioxane and leave them behind.
Now i left mine stirring overnight for the reaction to proceed.
And here we are the next day.
You can see it's quite thick with the polymerized impurities.
Now i recommend pouring this into a much larger flask to contain the foaming of our next step, fractional distillation.
Setup a fractional distillation column and distill off the dimethyl dioxane between 117-120 celsius and discard the rest.
And there we have it, dimethyl dioxane.
Now there isn't much data about long term storage.
But just from looking at it i think it's a strong peroxide former so i strongly recommend storing over sodium if you don't have an immediate use for it.
Okay, so now that we do have it, what can we use it for.
I'll be honest i don't know.
I originally tried making it to assist in my experiments for making sodium.
But it turned out dimethyl dioxane does not have the properties i desire.
It's boiling point, between 117-120 celsius, is not much higher than that of dioxane.
So it doesn't seem to be worth the effort when doing reactions that require heating.
But unlike dioxane, it doesn't seem to have high solubility in water, and in fact phase separates, while regular dioxane remains dissolved.
So dimethyl dioxane may be used as a liquid-liquid extraction solvent similar to diethyl ether.
It's highly polar but just non-polar enough to phase separate.
It has a much higher boiling point than ether and this may be useful when diethyl is too inconvenient
or if you plan to directly use the extracted solution in a higher temperature reaction.
The only major consideration is that dimethyl dioxane is indeed susceptible to acid catalyzed hydrolysis.
This is not a problem at room temperature but precludes higher temperature reactions if you're working under acidic conditions.
Oh well, i'll still keep my sample now that i've made it.
Maybe i'll find an actual use for it in the future.
Anyway, that is how you make dimethyl dioxane.
Thanks for watching.
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