Publications

Abstract The energetic study of benzoxazole, 5-chloro-2-methylbenzoxazole, and 2-chlorobenzoxazole, in condensed and gaseous states, has been developed using experimental techniques and computational approaches. The values of the standard (p degrees = 0.1 MPa) molar enthalpy of formation, at T = 298.15 K, of crystalline benzoxazole (36.0 +/- 2.0) kJ . mol(-1) and 5-chloro-2-methylbenzoxazole (145.6 +/- 2.2) kJ . mol(-1) and liquid 2-chlorobenzoxazole (52.5 +/- 3.0) kJ . mol(-1) were determined from the corresponding experimental standard molar energy of combustion in oxygen, -(3432.1 +/- 1.7) kJ . mol(-1), -(3883.0 2.0) kJ . mol(-1), and -(3298.0 +/- 2.8) kJ . mol(-1), respectively, measured by static or rotating-bomb combustion calorimetry. At T = 298.15 K, the standard (p degrees = 0.1 MPa) molar enthalpy of sublimation of benzoxazole and 5-chloro-2-methylbenzoxazole and of vaporization of 2-chlorobenzoxazole, (69.2 +/- 0.8) kJ . mol(-1), (82.4 +/- 2.2) kJ . mol(-1), and (56.3 +/- 1.6) kJ . mol(-1) respectively, were determined by a direct method, using the vacuum drop microcalorimetric technique. From the latter values and from the enthalpies of formation of the condensed compounds, the standard (p degrees = 0.1 MPa) enthalpies of formation of the gaseous compounds have been calculated. Standard ab initio molecular orbital calculations were performed using the G3(MP2)//B3LYP composite procedure and several working reactions in order to derive the standard molar enthalpy of formation of the three compounds. There exists a good agreement between the experimental and the computational data.

Abstract New strategies to reduce the environmental and economic costs of pesticides use are currently under study. Microencapsulation has been used as a versatile tool for the production of controlled release agricultural formulations. In this study, the photochemical degradation of the herbicides MCPA and mecoprop has been investigated in different aqueous media such as ultrapure and river water under simulated solar irradiation. To explore the possibility of introducing cyclodextrins in the herbicide formulations, the photodegradation study of the inclusion complexes of MCPA and mecoprop with (2-hydroxypropyl)-beta-cyclodextrin (HP-beta-CD) was also performed. The half-lives of MCPA and mecoprop inclusion complexes were increased approximately by a factor of three related to the free molecules. Additionally, it has been shown that the photodegradation of MCPA and mecoprop is influenced by their structural features. The additional methyl group existing in mecoprop molecular structure has a positive influence on the stabilization of the radical intermediate formed in the first stage of photodegradation of both herbicides. The results found indicated that MCPA and mecoprop form inclusion complexes with HP-beta-CD showing higher photostability compared to free herbicides indicating that HP-beta-CD may serve as ingredient in these herbicide formulations.

Abstract The standard molar enthalpies of formation, in the gaseous phase, at T = 298.15 K, of sarcosine, -(388.0 +/- 1.0) kJ . mol(-1), and sarcosine anhydride, -(334.5 +/- 1.6) kJ . mol(-1), were calculated by combining, for each compound, the standard molar enthalpy of formation, in the crystalline phase, and the standard molar enthalpy of sublimation, derived from measurements of the standard massic energies of combustion by static bomb combustion calorimetry, and from measurements of vapour pressures by the Knudsen mass-loss effusion method, respectively. The standard (p(o) = 0.1 MPa) molar enthalpies, entropies and Gibbs functions of sublimation, at T = 298.15 K, were also calculated. A theoretical study at the G3 and G4 levels has been carried out, and the calculated enthalpies of formation have been compared with the experimental ones.

Abstract Numerous studies in humans, animal models and cell lines have suggested the potential benefits from the consumption of green tea polyphenols, including prevention of cancer and heart diseases. However these potential effects have been strongly limited by green tea catechins low bioavailability, which hinders the development of therapeutic applications. In this review formulations that are being proposed for delivery of green tea catechins are discussed. New delivery systems are presented as valid alternatives to overcome the limitations such as green tea catechins poor stability or intestinal absorption.

Abstract In recent years, much attention has been given to dietary antioxidants, especially polyphenols. Several peptides derived from protein molecules have also been found to show antioxidant capacity along with other biological properties and thus there is an increasing interest in these compounds as health promoters. This review summarizes and discusses the main sources of antioxidative peptides with focus on food-derived peptides (animal, plant and marine sources), methods of preparation, antioxidant capacity evaluation as well as their proposed mechanisms of action. A discussion of the potential health effects and comments on the different applications for these antioxidants and their potential research interest are also subject of this review.

Abstract In the present work, the heat capacities at T = 298.15 K of 1,3-dialkylimidazolium bis(trifluoromethylsulfonyl)imide, [C(N/2)C(N/2)im][NTf2], were measured, for the first time, using a high-precision heat capacity drop calorimeter, with an uncertainty of less than 0.15%. Based on the obtained results, it was possible to evaluate the effect of the cation symmetry on the heat capacity data through a comparative analysis with the [C(N-1)C(1)im][NTf2] ionic liquid series. The molar heat capacities of the [C(N/2)C(N/2)im][NTf2] ionic liquids series present a less pronounced deviation from the linearity along the alkyl chain length than the asymmetric based ionic liquids series. Lower molar heat capacities for the symmetric than the asymmetric series were observed, being this difference more evident for the specific and volumic heat capacities. As observed for the [C(N-1)C(1)im][NTf2] series, a trend shift in the heat capacities at [C(6)C(6)im][NTf2] was found that reflects the impact of nonpolar region nanostructuration on the thermophysical properties of the ionic liquids. The profile of the two regions is in agreement with the expected effect arising from the nanostructuration in ionic liquids. The results obtained in the present work show a clear indication that for the symmetric series, [C(N/2)C(N/2)im][NTf2], the starting of the liquid phase nanostructuration/alkyl chain segregation occurs around [C(6)C(6)im][NTf2]. (C) 2013 AIP Publishing LLC.

Abstract Adhesion between rubber and leather is a crucial factor in the footwear industry. In the present work, three types of vulcanized styrene-butadiene rubbers (SBR) were modified using optimized atmospheric plasma jet treatment. Adhesion strength of SBR samples to leather, bonded by polyurethane (PU) adhesive, was evaluated and the ageing effect was studied. Plasma-treated rubbers were subjected to air ageing to evaluate the extent of hydrophobic recovery and the effect on the joint strength. Joint strength of the modified samples was evaluated by the T-peel test. The plasma treated surfaces were analyzed by means of contact angle measurements and scanning electron microscopy (SEM). The atmospheric plasma surface treatment significantly improves the wettability as well as adhesion of SBR. The ageing study showed a partial hydrophobic recovery of only one type of SBR, but the strength of adhesively-bonded joints between SBR surfaces and PU adhesive did not correspond with the ageing of plasma treatment.

Abstract In this work, the analytical use of facilitated ion transfer of catecholamines by dibenzo-18-crown-6 was investigated at the water/1,6-dichlorohexane interface using electrochemical methods (cyclic and square wave voltammetry). The experimental conditions for the analytical determination of noradrenaline and dopamine were established and detection limits of 1.7 and 0.35μM were obtained, respectively. The effect of excess ascorbic acid on the transfer and detection of the two catecholamines was investigated. The selectivity coefficients obtained for dopamine and noradrenaline in the presence of ascorbic acid were 3.5×10-4 and 2.5×10-3, respectively. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Abstract The stability of the UV filters 2-ethylhexyl-4-methoxycinnamate (EHMC) and 4-tert-butyl-4'-methoxydibenzoylmethane (BDM) in chlorinated water was studied. High-performance liquid chromatography (HPLC)-UV-diode array detection (DAD) was used to follow the reaction kinetics of both UV filters and HPLC-tandem mass spectrometry (MS/MS) was used to tentatively identify the major transformation by-products. Under the experimental conditions used in this work both UV filters reacted with chlorine following pseudo-first order kinetics: rate constant k = 0.0095 +/- 0.0007 min(-1) and half-life t(1/2) = 73 +/- 4 min for EHMC and rate constant k = 0.006 +/- 0.001 min(-1) and half-life t(1/2) = 119 +/- 14 min for BDM (mean +/- standard deviation). The chemical transformation of the UV filters in chlorinated water led to the formation of chlorinated by-products that were tentatively identified as mono- and dichloro-substituted compounds that resulted from substitution of the hydrogen atoms in the benzene rings by one or two chlorine atoms. Experimental Box-Behnken designs were used to assess the effect of experimental factors: pH, temperature, chlorine concentration, dissolved organic matter and artificial sunlight irradiation on the transformation of the UV filters.

Abstract The standard (p degrees = 0.1 MPa) molar enthalpies of formation, in the gaseous phase, of 2-, 3- and 4-bromobenzonitrile isomers were calculated from the combination of the following two parameters experimentally determined: the standard molar enthalpy of formation in the condensed phase, derived from the standard molar energy of combustion in oxygen at T = 298.15 K, measured by rotating-bomb combustion calorimetry, and the standard molar enthalpy of sublimation at the same reference temperature, derived from vapour pressure studies at several temperatures, as measured by mass-loss Knudsen effusion. The computational calculations complement the energetic study and analysis of the electron delocalization allows a comparison between the fluorine and bromine benzonitrile isomers. The harmonic oscillator model of aromaticity and nucleus-independent chemical shift aromaticity criteria and the natural bond orbital analysis were applied and related with the intramolecular enthalpic interactions. The intermolecular interactions in the crystal packing were analysed in terms of enthalpic and entropic contributions, using the crystallographic structures available in literature.