Examinando por Autor "Taravillo Corralo, Mercedes"

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Effects of high pressure on unsaturated fatty acids
(Taylor & Francis, 2014-09-24) Povedano, Isabel; Guignon, Berenguere; Rodríguez Montoro, Óscar; Sanz, Pedro Dimas; Taravillo Corralo, Mercedes; García Baonza, Mercedes
The objective of this study is to investigate the effects of high pressure processing on the molecular structure of some unsaturated fatty acids. Samples of elaidic acid, linoleic acid, ZE and EE conjugated linoleic acid are treated at 293 or 333 K at pressures up to 700 MPa. It is observed that the adiabatic heat generated from compression is able to bring the sample temperature above 373 K after 700 MPa. These relatively extreme conditions are of great interest for food sterilization, but they may induce undesirable change in fatty acid quality characteristics. To check for structural changes, Raman spectra of the samples are analysed after treatments. The comparison with Raman spectra of samples kept at atmospheric pressure shows that pressure induces some conformational changes at the hydrocarbon skeleton in solid samples, while the liquid ones remain unchanged. No cis/trans isomerization occurs, but gauche conformers are likely to be present.
Phase transitions and hindered rotation in dimethylacetylene at high pressures probed by Raman spectroscopy
(American Institute of Physics, 2004-12-08) García Baonza, Valentín; Rodríguez Montoro, Óscar; Taravillo Corralo, Mercedes; Cáceres Alonso, Mercedes; Núñez, Javier
We present Raman spectroscopy experiments in dimethylacetylene ~DMA! using a sapphire anvil cell up to 4 GPa at room temperature. DMA presents phase transitions at 0.2 GPa ~liquid to phase I! and 0.9 GPa, which have been characterized by changes in the Raman spectrum of the sample. At pressures above 2.6 GPa several bands split into two components, suggesting an additional phase transition. The Raman spectrum of the sample above 2.6 GPa is identical to that found for the monoclinic phase II (C2/m) at low temperatures, except for an additional splitting of the band assigned to the fourfold degenerated asymmetric methyl stretch. The global analysis of the Raman spectra suggests that the observed splitting is due to the loss of degeneracy of the methyl groups of the DMA molecule in phase II. According to the above interpretation, crystal phase II of DMA extends from 0.9 GPa to pressures close to 4 GPa. Between 0.9 and 2.6 GPa, the methyl groups of the DMA molecules rotate almost freely, but the rotation is hindered on further compression.
Pressure as driving force in the formation of Fossil Resins: Pressure Induced Changes in trans-Communic Acid studied by Raman Spectroscopy
(IOP PUBLISHING, 2017-01-01) Rodríguez Montoro, Óscar; Taravillo Corralo, Mercedes; Povedano, Isabel; Tortajada Pérez, José; García Baonza, Valentín
The main purpose of this study is to provide spectroscopic evidence of possible chemical pathways in the formation of fossil resins under high pressure conditions. In this work, we have studied trans-communic acid (majority precursor compound in resinites) under high pressure conditions by using a sapphire anvil cell. Raman spectra were measured at atmospheric pressure up to 8 GPa (at room temperature). Slight changes were observed in the spectra. Furthermore, the recovered sample after pressure release was analyzed by FTIR. Our results are not conclusive about a possible chemical pathway of polymerization induced by pressure.
Raman spectroscopic study of the formation of fossil resin analogues
(Wiley, 2014-08-25) Rodríguez Montoro, Óscar; Taravillo Corralo, Mercedes; San Andrés, Margarita; de la Roja de la Roja, José Manuel; Fernández Barrero, Alejandro; Arteaga; García Baonza, Valentín
The purpose of this work is to provide spectroscopic evidence of possible chemical pathways that took place in the formation of fossil resins Class I. The natural polymerization process is mimicked in the laboratory using pure communic acids (terpene derivatives) as reactants, which were subjected to controlled temperature treatment. We shall focus here on the trans-, cis- and iso-/ mirceo- communic acid isomers, and the temperature-induced reactivity is discussed on the basis of the different arrangements of the conjugated double-bonds moieties in the monomeric units. Transformations starting at 130, 90 and 127 °C, for trans-, cis- and iso-communic acids, respectively, led to the formation of intermediate products. The whole process was followed and analyzed by micro-Raman spectroscopy. The absence of several Raman signatures suggests conjugation loss in the side-chain of these intermediate compounds. With increasing temperature, the intermediate products suffer additional maturation reactions to form the final fossil resin analogues object of this work.
Theoretical (DFT) and experimental (Raman and FTIR) spectroscopic study on communic acids, main component of fossil resins
(Elsevier, 2019-07-19) Rodríguez Montoro, Óscar; Tortajada Pérez, José; Lobato Fernández, Álvaro; García Baonza, Valentín; Taravillo Corralo, Mercedes
The objective of this work is to establish a spectral assignment of several communic acids. The most significant vibrational modes of three stereoisomers of communic acids [trans-, cis-, and iso- (or mirceo-)] are presented. They are showed throughout experimental Raman and IR spectra, and on the basis on calculations with Density Functional Theory (DFT) and the assignment of the spectral bands of different resins found in the literature. These three communic acids studied are the most important isomers present in the scaffold of the fossil resins Class I, as monomers or co-polymerized according to several authors. These kinds of terpenes are used as starting material, for example, for the synthesis of the fungicide and compounds bioactives. In a novel way, it is reported jointly the assignment of the experimental Infrared and Raman modes together with theoretical modes, since normally the authors tend to focus on one or another spectroscopic technique only. These results can be used as a reference for distinguishing amber from less matured resins as copal, determining the local origin of archaeological fossilized resins. Moreover, they will serve as help to differentiate between real and imitation ambers.