[Zurück]

M. López Pastor, A. Domínguez-Vidal, M.J. Ayora-Cañada, M. Valcárcel, B. Lendl:
"In-situ Raman spectroscopic study of base catalyzed di- and trimerisation of malodinitrile in ionic liquids";
Poster: XX. Reunion Nacional de Espectroscopia, Ciudad Real, Spanien; 10.09.2006 - 15.09.2006.

In chemical research and technology there is a continued interest in Room Temperature Ionic Liquids (RTILs) due to their interesting physico-chemical properties, such as negligible vapor pressure (even at elevated temperature), non flammability or good electrical conductivities, among others. Therefore, RTILs have been used as solvents or co-solvents in chemical synthesis where they hold promise to substitute conventional organic solvents in certain applications. By this way, the reaction between malononitrile and potassium hydroxide (KOH) in water and in 1-ethyl-3-methylimidazolium tetrafluoroborate (emimBF4) has been studied by Raman microspectroscopy and compared respectively. Malononitrile is widely used in chemical synthesis especially in Knoevenagel condensations as well as Michael additions because of its exceptional reactivity due to its acid protons. Upon reaction with bases malononitrile form a carbanion acting as reactive intermediate. Two Dimensional Correlation Spectroscopy (2DCoS) and Multivariate Curve Resolution (MCR) have been used to analyze the in-situ recorded Raman spectra. In both studied systems the carbanion, which is formed by deprotonation of malononitrile, could be detected spectroscopically. In addition, the formation of a dimer can be detected in both systems. Furthermore, a trimer, formed by a subsequent Michael addition, can be detected when aqueous solution was used as reaction media. Based on the spectra of the pure components and concentration profiles obtained from MCR analysis, the reaction intermediates, as well as the products, could be identified. 2DCoS was very helpful in corroborating these results.