Sciencemadness Discussion Board

Carbonate ester synthesis from urea?

EverythingAl2O3 - 15-1-2021 at 06:50

I know that carbonate esters are typically made from the reaction of phosgene and alcohols. I don't exactly have the equipment to handle phosgene, but think it would be fun to synthesize and play with them in grignard reactions and maybe an attempt to make polycarbonates (making my own glasses lenses sounds like a fun long-term project).

Urea seems like the easiest OTC source of the carbonate structure. The biggest issue I see is that amides are more stable than esters so conversion from amide to ester will be particularly difficult, and that water/hydroxide will ruin the reaction. I think that the use of sodium/potassium methoxide in methanol (because methanol doesn't form an azeotrope with water it can be easily purified) and refluxed for a period of time (maybe 24 hours). I know n-butanol can do this at high temperature according to this paper at temps around 175-190C so I'm hoping alkoxides will help speed up the reaction at lower temps.

I will be personally attempting this once I get some urea and sodium/potassium metal to make pure alkoxides. Will probably use nurdrages magnesium reduction method for it. As an additional side project I might attempt to make a super efficient high boiling alcohol catalyst based on his previous work to see if I can beat the 10 hours of borneol for generating sodium and see just how fast potassium can be made. And I will try to also capture the NH3 and store it as NH4Cl cuz if I'm gonna work with useful nasty smelling chemicals by god I'm gonna make sure I don't have to smell them.

And now I have issued myself a huge challenge that I hope to be able to achieve being new to actual synthesis of chemicals.

Attachment: Carbamic Esters from Urea.pdf (356kB)
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njl - 15-1-2021 at 07:16

As discussed in other threads, simple carbonate esters can be made simply from the alcohol and urea in moderate yields. I bet you could even incorporate Al2O3 into the reaction if you look around enough. I have tried this reaction between methanol and urea. Fairly uneventful reaction, but using such low boiling alcohols makes the reaction take ages. So maybe catalytic alkoxide would help. Point being, you don't need a bunch of sodium to get this reaction to work.

EverythingAl2O3 - 15-1-2021 at 09:08

Quote:

As discussed in other threads, simple carbonate esters can be made simply from the alcohol and urea in moderate yields. I bet you could even incorporate Al2O3 into the reaction if you look around enough. I have tried this reaction between methanol and urea. Fairly uneventful reaction, but using such low boiling alcohols makes the reaction take ages. So maybe catalytic alkoxide would help. Point being, you don't need a bunch of sodium to get this reaction to work.

You are right it looks like Al2O3 can be used. I'm not sure what preparation method of the y-Al2O3 needs to be used. I'll need to search through the references. It seems to have low yields though.

Attachment: Synthesis of organic carbonates from alcoholysis.pdf (3.5MB)
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BromicAcid - 15-1-2021 at 17:23

I did a few trials to make ethylene carbonate in a different life, the results looked promising but like most of my early work I focused more on the synthesis than the workup:

http://www.sciencemadness.org/talk/viewthread.php?tid=2948