Sciencemadness Discussion Board

Simple question about making carbonates of primary amines

FormicAcidAnimal - 29-10-2015 at 17:59

Hi there!
I'm currently wondering what carbonates of primary amines look like.
According to this thread http://www.sciencemadness.org/talk/viewthread.php?tid=2099 you can simply make them by gassing CO2 into freebase using a dry solvent, at least in the case of trypamines.

Little quote from US2943093
Quote:

... are dissolved in 320 cc. of absolute ethanol at 40 C... Gaseous carbon dioxide (CO2) is passed through the solution while cooling to such an extent that the temperature duringreaction does not exceed 40 C... After passingcarbon dioxide through the solution at 40 C. for 20 minutes; the reaction mixture is cooled to about +5°C., and introduction of carbon dioxide is continued at said temperature rfor 30 more min-v utes. The-precipitated compound is filtered with suction, washed with absolute alcohol, and dried in the open....


Now I'm wondering very much how this carbonate looks like?
Cabonates are usually CO3 2-, right?
So the product should look (R-NH3)CO3(H3N-R)
Now I'm wondering how it's even possible to form carbonates from plain dry CO2 in the abscence of H2O? Or how do these primary amine carbonates are supposed to look like? Are they really "carbonates", I guess not, right? How are they called?

Maybe I only can't see the tree because the forest is in the way?
If so, please move this post to beginners section ;)
But thank you in advance anyway!

[Edited on 30-10-2015 by FormicAcidAnimal]

Crowfjord - 29-10-2015 at 18:44

I think they are actually amine carbamates, i.e. R-NHCO2 - NH3-R+. Search the forum, I'm pretty sure I learned this from a post here, possibly by Nicodem.

[Edited on 30-10-2015 by Crowfjord]

FormicAcidAnimal - 29-10-2015 at 20:15

Ahh thank you, carbamic acid + salt makes a lot more sense!

R-NH-CO-O(-) (+)H3N-R

Though I wonder about how the mechanism works and about stability in practice.
Searching the forum for "carbamat" etc. unfortunately didn't find very much

And I wonder if carbamates could be reduced with NaBH4, LAH etc. to R-NH-CH2-OH... (or even tertiary or quarternary in one step)


EDIT: I think I will have to buy a soda stream with glas bottles ;)





[Edited on 30-10-2015 by FormicAcidAnimal]

clearly_not_atara - 30-10-2015 at 08:17

The third paragraph of US 2943093 states:
Quote:
The compounds formed thereby which are stable at room temperature consist of a comibnation of 2 moles of the tryptamine compound and 1 mole of carbon dioxide according to elementary analysis. Thus, said addition products represent apparently the tryptamine salt of the N-tryptamino carboxylic acid of Formula II V R CH:


Carbamic acids generally decompose spontaneously in acid to release the amine.

Dr.Bob - 30-10-2015 at 10:35

Carbonate salts are not very stable in general, but many organic bases will form them to some degree, which is one way that systems trap CO2 for global warming prevention, as the carbonates release CO2 later very easily, often with any heat or acid.

Carbamates (R-NC(=O)-R) are completely different than carbonate salts, and can be quite stable. Some, like benzyl carbamates are very stable to acids or bases.