Raquel Montón

Polytechnical University of Valencia, Valencia, Valencia, Spain

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Publications (6)9.75 Total impact

  • [show abstract] [hide abstract]
    ABSTRACT: A series of bifunctional organic catalysts containing acid and basic sites with ionic liquid characteristics have been prepared and their catalytic activity and reaction coordinate for aldol and Knoevenagel condensations have been compared. While the only factor controlling catalyst activity for the Knoevenagel condensation was the distance between the acid and base sites, the spatial orientation of the organocatalyst is also key to achieve high activity and selectivity in the Claisen-Schmidt condensation. Mechanistic studies based on theoretical DFT calculations show that the acid-base bifunctional organocatalyst follows a mechanism inspired in natural aldolases for the synthesis of trans-chalcones, being able to produce a large variety of these compounds of industrial interest. The combination of the acid-base pairs within the proper geometry and the ionic liquid nature makes this catalyst active, selective and recyclable.
    Physical Chemistry Chemical Physics 08/2011; 13(38):17255-61. · 3.83 Impact Factor
  • [show abstract] [hide abstract]
    ABSTRACT: By partial exchange of surface protons of a polyoxometalate (POM; H5PO40V2Mo10) by an ionic liquid (IL; butylmethylimidazolium, bmim+), a protonic IL-POM ([bmim]4HPO40V2Mo10) was obtained. Further exchange of this material with Pd2+ yields a final solid that HRTEM and EXAFS-XANES techniques show to be formed by very regular nanoparticles of PdO with 2 nm diameter, which are supported on 1 μm particles of IL-POM hybrid material. The PdO nanoparticles can be easily reduced to Pd, and the resultant material is an active and selective catalyst for the Heck reaction. The catalyst can be recycled, though metal leaching occurs in polar solvents. This can be an interesting material for performing Pd-catalyzed reactions in nonpolar solvents or for working in gas-phase reactions.
    Journal of Physical Chemistry C - J PHYS CHEM C. 04/2010; 114(19).
  • [show abstract] [hide abstract]
    ABSTRACT: The Beckmann rearrangement of cyclododecanone oxime into ω-laurolactam has been investigated in four ionic liquids: 1-butyl-3-methylimidazolium hexafluorophosphate and tetrafluoroborate ([C4mim]+PF6-, [C4mim]+BF4-), and 1-butyl-2,3-dimethylimidazolium and 1-butyl-4-methylpyridinium hexafluorophosphates ([C4mpyr]+PF6-, [C4m2im]+PF6-), in a batch reactor as well as by ‘in situ’ multinuclear solid-state NMR spectroscopy. The Beckmann rearrangement reaction of cyclododecanone oxime takes place in [C4mim]+PF6- and [C4mpyr]+PF6- with excellent activity and selectivity, while practically null activity is observed in [C4m2im]+PF6- and [C4mim]+BF4-. The results obtained indicate that a very low level of hydrolysis of the PF6- anion in [C4mim]+PF6- and [C4mpyr]+PF6- occurs under reaction conditions (130°C), and the HF formed at the level of ppm acts as catalyst in the Beckmann rearrangement with excellent conversion and selectivity.
    Journal of Catalysis - J CATAL. 01/2010; 275(1):78-83.
  • [show abstract] [hide abstract]
    ABSTRACT: Bifunctional acid-base ionic liquid organocatalysts with different distances between the two sites have been synthesised, and their activity for the Knoevenagel condensation has been tested. As has been found to be the case with enzymes, the distance between the acidic and basic sites determines the activity of the bifunctional organocatalyst, and at the optimal distance the reaction rate increases by two orders of magnitude with respect to the purely acidic or basic counterpart organocatalysts. The experimental results have been rationalised through the study of the reaction mechanism of the Knoevenagel condensation between malononitrile and benzaldehyde by means of DFT calculations. It has been found that it consists of two consecutive steps. First, deprotonation of malononitrile on the basic site to obtain a methylene carbanion intermediate takes place, and second, co-adsorption and activation of benzaldehyde on the acid centre of this intermediate followed by the C-C bond-formation reaction. The calculations and the kinetic study indicate that there is an inversion of the rate-controlling step when the distance between the acidic and the basic sites is modified, with a direct implication on the reaction rate.
    Chemistry 12/2009; 16(4):1221-31. · 5.93 Impact Factor
  • [show abstract] [hide abstract]
    ABSTRACT: The Beckmann rearrangement of the relatively bulky cyclododecanone oxime was carried out in batch and fixed-bed continuous reactors. With microporous molecular sieve catalysts, the process is controlled by diffusion within the micropores. Conversion, selectivity, and catalyst life are improved with the use of nanocrystalline materials. A solid acid catalyst formed by nanolayers of zeolite is more active and selective than either a nanocrystalline Beta zeolite or a mesoporous MCM-41 material, and the amount of organic remaining adsorbed on the catalyst after reaction is smaller in the former. Product desorption, activity, selectivity and catalyst life are much improved by using a nonprotic polar solvent and higher reaction temperatures.
    Journal of Catalysis. 01/2007; 250(1):161-170.
  • Aida Vila, Raquel Montón
    Greenpeace: Boletín informativo trimestral, Nº. 2, 2008, pags. 42-43.