Formation of carbamic acid in organic solvents and in supercritical carbon dioxide

The behavior of amines in various CO 2-rich solvents is described. 1H and 13C NMR spectra in DMSO, chloroform, and benzene show that the amines are completely converted into carbamic acid by just bubbling atmospheric CO 2 through the solution. However, the chemical shifts of several protons and the...

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Bibliographic Details
Published in:The Journal of supercritical fluids 2007-05, Vol.41 (1), p.109-114
Main Authors: Dijkstra, Z.J., Doornbos, A.R., Weyten, H., Ernsting, J.M., Elsevier, C.J., Keurentjes, J.T.F.
Format: Article
Language:English
Subjects:
Amine
Carbamic acid
NMR
Supercritical CO 2
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Summary:The behavior of amines in various CO 2-rich solvents is described. 1H and 13C NMR spectra in DMSO, chloroform, and benzene show that the amines are completely converted into carbamic acid by just bubbling atmospheric CO 2 through the solution. However, the chemical shifts of several protons and the carbonyl 13C in the newly formed compounds strongly depend on the organic solvent used. FT-IR measurements confirm the observation that carbamic acid formation occurs. Changing the solvent to supercritical CO 2 shows a temperature- and pressure-dependent equilibrium between the amine and the carbamic acid; higher pressures shift the equilibrium towards the carbamic acid, whereas higher temperatures favor the free amine.
ISSN:0896-8446
1872-8162
DOI:10.1016/j.supflu.2006.08.012