resumo
Controversy behind the Postulation that ionic liquids (ILs) are entirely green materials emerged a few years ago. This statement is not always valid, and properties Such as toxicity and chemical/thermal stability of ILs should be fully characterized to evaluate their potential use as green solvents. Therefore, in this work, the thermal and chemical decompositions of hexafluorophosphate- and tetrafluoroborate-based ILs in aqueous solutions were evaluated. The experimental conditions employed allowed the Study of the possible decomposition of both anions, the effect of the cation side alkyl chain length, the influence of the pH of the aqueous Solutions, as well as the temperature influence. Three experimental techniques were employed to fully characterize those anions' stability, electrospray mass spectrometry, nuclear Magnetic resonance spectroscopy, and pH measurements Of the equilibrium aqueous Solutions. The results noticeably indicate that it is suitable to use aqueous solutions of hexafluorophosphate-based ILs at moderate temperatures while acidic conditions promote the anion hydrolysis, even at low temperatures. Oil the other hand, the tetrafluoroborate-based ILs are not water-stable compounds since they hydrolyze under all of the conditions tested and the hydrolysis extent is markedly dependent on the temperature.
palavras-chave
MUTUAL SOLUBILITIES; WATER; COMPLEXES
categoria
Chemistry; Physics
autores
Freire, MG; Neves, CMSS; Marrucho, IM; Coutinho, JAP; Fernandes, AM
nossos autores
Catarina Maia Seco Seiça Neves
Investigador Auxiliar
Isabel Maria Delgado Jana Marrucho Ferreira
Professor Catedrático
Mara Guadalupe Freire Martins
Investigador CoordenadorGrupos
G4 - Materiais Renováveis e Economia Circular
G5 - Materiais Biomiméticos, Biológicos e Vivos
agradecimentos
The authors thank financial support from Fundacao para a Ciencia e a Tecnologia (Project PTDC/EQU-FTT/65252/2006). In addition, the authors acknowledge Prof. K. R. Seddon for calling their attention for (lie instability of [BF