On the spontaneous carboxylation of 1-butyl-3-methylimidazolium acetate by carbon dioxideElectronic supplementary information (ESI) available: Detailed experimental conditions, Raman and NMR spectroscopic assignments. See DOI: 10.1039/c1cc16702b

The formation of 1-butyl-3-methylimidazolium-2-carboxylate in the mixture of CO 2 with 1-butyl-3-methylimidazolium acetate under mild conditions (298 K, 0.1 MPa) has been put in evidence in the liquid phase using Raman and infrared spectroscopy complemented by DFT calculations and NMR ( 1 H, 13 C, 15 N) spectroscopy. Carboxylation reaction of 1-butyl-3-methylimidazolium with CO 2 under mild conditions (298 K, 0.1 MPa) has been put in evidence in the liquid phase using Raman, infrared and NMR spectroscopy and complemented by DFT calculations.