Chemistry, Physical and Theoretical Chemistry, Environmental Chemistry
29
Scopus Publications
Scopus Publications
Aqueous-Phase Degradation Mechanism of Parabens, Emerging Contaminants, by Peroxynitrite Clara I. Alcolado, Elena Jiménez, Luis García-Río, Francisco J. Poblete ACS Es and T Water, 2025 High Resolution Image Download MS PowerPoint Slide Advances in science and technology have improved the quality of life but have also contributed to environmental pollution through additives like parabens, commonly used as preservatives in personal care products. This study investigates the degradation of a series of parabens (methylparaben, ethylparaben, propylparaben, and butylparaben) in aqueous-phase solution initiated by peroxynitrous acid (HOONO), an oxidant present in environmental waters. A stopped flow system was employed to follow this oxidation reaction. A reaction mechanism, considering experimental variables, such as pH, temperature, ionic strength, radical scavengers, and reaction products detected, was proposed. This mechanism involves two competitive pathways: a radical attack producing hydroquinone and quinone and a nucleophilic attack by HOONO yielding p -hydroxybenzoic acid, a less ecotoxic compound than parabens. The acidic equilibrium constants of the carbonyl group of parabens and the rate constants for the nucleophilic attack of HOONO on parabens were experimentally determined. Additionally, a structure–reactivity correlation analysis (QSAR) through the Taft equation was applied for the determined equilibrium and nucleophilic attack rate constants. The derived QSAR can be applied to other water-soluble parabens.
Aromatic aldehyde oxidation by hexacyanoferrate(III) catalyzed by Ru(VI) in alkaline medium C.I. Alcolado, J. Poblete, L. García-Río, E. Jiménez, F.J. Poblete Journal of Molecular Liquids, 2024 In this study, the selective oxidation of aromatic aldehydes has been investigated using Ru(VI) as a catalyst and hexacyanoferrate (III) as a cooxidant in an alkaline medium. The reaction order with respect to the oxidant and the aromatic aldehyde is complex while the reaction order with respect to Ru(VI) is one. The proposed mechanism presents two catalytic cycles for the two active species of the catalyst. In each cycle, Ru(VI) species forms a complex with the anion of hydrated benzaldehyde which decomposes to form benzoic acid. The function of hexacyanoferrate(III) is the regeneration of catalyst species. A quantitative structure–activity relationship was analyzed using the Hammett equation for decomposition complex step. This analysis showed that deactivating groups in para- position enhances this process.
Oxidation of Aldehydes Used as Food Additives by Peroxynitrite Clara I. Alcolado, Luis Garcia-Rio, Juan C. Mejuto, Inmaculada Moreno, Francisco J. Poblete, et al. Antioxidants, 2023 Benzaldehyde and its derivatives are used as food supplements. These substances can be used mainly as flavorings or as antioxidants. Besides, peroxynitrite, an oxidizing agent, could be formed in canned food. Both species could react between them. The present article has focused on the kinetic study of the oxidation of aldehydes by peroxynitrite. A reaction mechanism that justifies all the experimental results is proposed. This mechanism, in acidic media, passes through three competitive pathways: (a) a radical attack that produces benzoic acid. (b) peracid oxidation, and (c) a nucleophilic attack of peroxynitrous acid over aldehyde to form an intermediate, X, that produces benzoic acid, or, through a Cannizzaro-type reaction, benzoic acid and benzyl alcohol. All rate constants involved in the third pathway (c) have been calculated. These results have never been described in the literature in acid media. A pH effect was analyzed.
Archaeometric characterization of the ceramics from two celtiberian hillforts: Preliminary results Álvaro Sánchez Climent, Carlos J. Sánchez Jiménez, F. J. Poblete, María Luisa Cerdeño Serrano Mediterranean Archaeology and Archaeometry, 2018 In this work, we present the preliminary results of the archaeometric analysis of several ceramic and clay samples from two Celtiberian hillforts of the Iron Age from the Spanish Central Plateau: El Ceremeño and its cemetery (Early and Middle Iron Age) and the oppidum of Los Rodiles (Late Iron Age) including La Rodriga, a potter's workshop contemporary to Los Rodiles. Clay samples were collected from all sites in order to carry out a provenance analysis and to determine if the ceramic production of the proposed archaeological sites was local or foreign. Mineralogical analysis was performed by Thin-Layer Petrography (TLP) and XRay Diffraction (XRD), whereas chemical analysis was done by X-Ray Fluorescence: Semi-quantitative (XRF) and Trace Elemental analysis (XRF-t). Moreover, to complete the study a thermal analysis was carried out by a dilatometer (DLT). Although the number of samples evaluated was limited, in all the studied cases, the analyzed pottery was clearly found to be made with the clay from the surroundings of the archaeological sites.
Electrostatic repulsion between cucurbit[7]urils can be overcome in [3]pseudorotaxane without adding salts M. Pessêgo, J. A. Moreira, A. M. Rosa da Costa, P. Corrochano, F. J. Poblete, et al. Journal of Organic Chemistry, 2013 The host-guest chemistry between cucurbit[7]uril (CB7) and a series of bolaform (Bn) surfactants with different chain lengths, n = 12-22, was the target of our study. [3]Pseudorotaxanes are formed when the alkyl chain of the bolaform has more than 14 carbon atoms. In these cases, two CB7 molecules can be accommodated between the two head groups of the bolaform without addition of electrolytes to the medium. In the case of a bolaform with 12 carbon atoms, the electrostatic repulsion between the carbonyl groups of the CB7 molecules avoids the threading of a second CB7 molecule yielding a mixed structure formed by a [2]pseudorotaxane and an external host-guest complex. The assembly behavior was investigated using NMR spectroscopy, isothermal titration calorimetry (ITC), and kinetic measurements.
