| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1236550 | Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy | 2011 | 10 Pages |
Aqueous solutions of sodium tribromoacetate (NaCBr3CO2) and its corresponding acid (CBr3COOH) have been studied using Raman and infrared spectroscopy. The spectra of the species in solution were assigned according to symmetry Cs. Characteristic bands of CBr3CO2−(aq) and the tribromoacetic acid, CBr3COOH(aq), are discussed. For the hydrated anion, the CO2 group, the symmetric CO2 stretching mode at 1332 cm−1 and the asymmetric stretching mode at 1651 cm−1 are characteristic while the CO mode at 1730 cm−1 is characteristic for the spectra of the acid. The stretching mode, νC–C at 912 cm−1 for CBr3CO2−(aq) is 10 cm−1 lower in the anion compared with that of the acid. These characteristic modes are compared to those in acetate, CH3CO2−(aq). Coupling of the modes are fairly extensive and therefore DFT calculations have been carried out in order to compare the measured spectra with the calculated ones. The geometrical parameters such as bond length and bond angles of the tribromoacetate, and tribromoacetic acid have been obtained and may be compared with the ones published for other acetates and their conjugated acids.CBr3COOH(aq) is a moderately strong acid and the pKa value derived from quantitative Raman measurements is equal to −0.23 at 23 °C. The deuterated acid CBr3COOD in heavy water has been measured as well and the assignments were given.
Graphical abstractRaman spectra of aqueous tribromoacetic acid and its salt. Upper panel: NaCBr3CO2, and lower panel: CBr3COOH. Note, that all three scattering components are given: polarized, depolarized and the isotropic.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Solutions of NaCBr3CO2 and CBr3COOH were measured using Raman and infrared spectroscopy. ► The vibrational modes of species CBr3CO2−(aq), CBr3COOH(aq), and CBr3COOD(D2O) were assigned. ► Calculated frequencies by the DFT method were compared with the measured ones. ► Characteristic modes have been indentified for CBr3CO2−(aq), and CBr3COOH(aq). ► The pKa value for the moderately strong acid, CBr3COOH(aq) has been obtained at −0.23 (23 °C).
