Sciencemadness Discussion Board

diethyl carbonate (NO PHOSGENE)

hasani10 - 11-11-2020 at 10:37

Can anyone suggest an alternate route to diethyl carbonate that doesn't require the use of phosgene?

Exactly how dangerous is phosgene? My unwillingness to use it comes from safety concerns, i have no fume hood, just a well ventilated outdoor space, and i'm guessing that's TOTALLY not enough protection.

I thought if i were to follow the phosgene route i may reduce phosgene exposure off by forming it in-situ; bubbling air through chloroform and ethanol mixture. If done in a closed system then perhaps a phosgene trap could also be set up for any excess that doesn't react?

njl - 11-11-2020 at 10:47

I think urea and ethanol can react to ethyl carbamate, so maybe you could go one step further and get the carbonate.

Fyndium - 11-11-2020 at 11:19

If you were in absolute need to do some hazardous work, make a fume hood from tarp or construction plastic and wood and get a duct fan and few meters high plastic tube as chimney. This is trivial to do outdoors because you don't have to make separate exhaust system, just make the air move to proper direction. I did that ages ago when I was working with cyanides. Unless you spill or blow something up, there's no chance of you getting a whiff.

Mere outdoors can be more hazardous than one thinks. I've had to relocate myself several times because of wind during every single experiment to get away from the toxic plume when I was for example evaporating or heating up something. And this is with something moderately toxic. Never handled HCN or the more toxic stuff. One whiff and you're done.

Swinfi2 - 11-11-2020 at 12:59

I found this while looking for a ethylene carbonate synthesis a while back, it uses easy to acquire reagents that are pretty safe and I'm pretty sure substituting methyl and ethyl alcohol should work fine.

https://doi.org/10.1039/B304182D

If you get stuck at the paywall let me know.

My experience of the first reaction is that it works poorly without vacuum and an uncertain ammonium salt can block the ammonia leaving, then pressure will pop your equipment open. But at least the catalyst is easy to get hold of.

[Edited on 11-11-2020 by Swinfi2]

Fyndium - 11-11-2020 at 13:12

Sci-Hub takes care of paywalls, FYI.

hasani10 - 11-11-2020 at 16:34

Awesome!

I'll be having a go at the ethylene glycol route i think, soon as i get some more ethanol.

Thanks for all the suggestions :D

Can't believe i've never seen sci-hub before, that's awesome! Luckily i've started uni this year so a lot more has opened up for me, but still finding loads of papers that i need to pay for, this will help alot :)


[Edited on 12-11-2020 by hasani10]

Cou - 11-11-2020 at 17:03

You can buy diethyl carbonate and dimethyl carbonate on ebay

clearly_not_atara - 11-11-2020 at 18:24

So I'm not sure if you're aware, but ethylene glycol and urea makes ethylene carbonate, not diethyl carbonate.

Also, the reaction with urea doesn't work very well with ethanol, because it won't get hot enough and you need ammonia to distill away. But you can I think distill diethyl carbonate out of a solution of ethylene carbonate in NaOEt/ethanol or maybe even KOH/ethanol.

artemov - 11-11-2020 at 20:42

I thought you need high temp, high pressure and catalyst to get from the carbamates to the carbonates?

I was just looking at this yesterday, trying to find a way to get ammonia from urea without using my precious hydroxides :D

Attachment: shukla2017.pdf (3.5MB)
This file has been downloaded 129 times

[Edited on 12-11-2020 by artemov]

Metacelsus - 12-11-2020 at 03:47

Ethyl carbamate is a known carcinogen, so be careful.

Swinfi2 - 12-11-2020 at 12:34

I also made the mistake of attempting to capture the ammonia because why not... this would have been fine but I didn't have the capability of stirring the ammonia trap and a thin layer of over-concentrated ammonia blocked absorption from the bulk as it floats. Swirling helps but it wouldn't be my first choice.

Also my other post could have been a bit clearer but two reaction steps is a good trade off for avoiding war-gas as was the intent of OP. Overall scheme:

Screenshot_20201112-202413_Adobe Acrobat.jpg - 36kB

Abromination - 12-11-2020 at 14:14

Quote: Originally posted by Fyndium  
If you were in absolute need to do some hazardous work, make a fume hood from tarp or construction plastic and wood and get a duct fan and few meters high plastic tube as chimney. This is trivial to do outdoors because you don't have to make separate exhaust system, just make the air move to proper direction. I did that ages ago when I was working with cyanides. Unless you spill or blow something up, there's no chance of you getting a whiff.

Mere outdoors can be more hazardous than one thinks. I've had to relocate myself several times because of wind during every single experiment to get away from the toxic plume when I was for example evaporating or heating up something. And this is with something moderately toxic. Never handled HCN or the more toxic stuff. One whiff and you're done.

Not that it seems like op is interested in the phosgene route, but this is absolutely not suitable for anything with that sort of LD50. Infact, it seems moronically stupid to work with phosgene in any sort of home fume hood, even if it works well.

hasani10 - 13-11-2020 at 02:47

Thank you for the clarification Abromination, after a bit of googling it does seem like a resolute 'fuck that' to any work involving phosgene.

Swinfi2 The first reaction in that paper sounds reproducible (EG and urea to EC), but i'm unsure about the second (EC and, in my case ethanol, to DEC) as it's run in an autoclave at 150C for 4 hours; i'm not sure simply refluxing would be sufficient, what do you reckon?

https://www.sciencedirect.com/science/article/pii/S156673671...
This paper mentions alkaline earth metal oxides can be used as catalysts, so maybe i'll distill off EC and try the reaction refluxing with CaO and ethanol.

Swinfi2 - 13-11-2020 at 09:13

I'm not 100% sure with Diethyl carbonate, however most transesterification reactions are an equilibrium so you would want plenty of ethanol and minimal water.

Im guessing they use heat and pressure to avoid contamination on their analysis but a more typical catalyst is acid or base with reflux. In this case the acid part of the di-ester is CO2 so I think you would probably do better with base over acid as acid may promote decomposition. Also DEC/DMC/EG are common battery electrolytes so should tolerate alkaline conditions.

Can't guarantee it will work but I would try:
1eq EG + 10eq EtOH + 0.1eq NaOH -(reflux)-> Products
NaOEt may work better as the catalyst if you can get/make it but I hear that can be tricky.

As for the paper, CaO seems like a good option as it would destroy water, but heterogeneous catalysts suffer poor contact area. On the other hand it would make the workup easier as you can just filter it.

[Edited on 13-11-2020 by Swinfi2]