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Binary alcohol + ether liquid mixtures are of significant importance as potential biofuels or additives for internal combustion engines and attract considerable fundamental interest as model systems containing one strongly H-bonded self-associating component (alcohol) and one that is unable to do so (ether), but that can interact strongly as a H-bond acceptor. In this context, the excess thermodynamic properties of these mixtures, specifically the excess molar enthalpies and volumes (H-E and V-E), have been extensively measured. Butanol isomer + di-n-butyl ether (DBE) mixtures received significant attention because of interesting differences in their V-E, changing from negative (1- and isobutanol) to positive (2- and tert-butanol) with increasing alkyl group branching. With the aim of shedding light on the differences in alcohol self-association and cross-species H-bonding, considered responsible for the observed differences, we studied representative 1- and 2-butanol + DBE mixtures by molecular dynamics simulations and experimental excess property measurements. The simulations reveal marked differences in the self-association of the two isomers and, while supporting the existing interpretations of the H-E and V-E in a general sense, our results suggest, for the first time, that subtle changes in H-bonded topologies may contribute significantly to the anomalous volumetric properties of these mixtures.

Nuclear Magnetic Resonance (NMR) methodologies offer a comprehensive characterization of foodstuffs owing to the possibility to study a sample from different points of view including structural, compositional, functional, morphological etc. aspects. High resolution NMR spectroscopy applied to semi-solid food samples or to extracts in solution is used to determine the foodstuff composition. Here, some features of high resolution NMR methodologies related to food analysis such as quantitative analysis, chemometrics, and use of databases are included. Other NMR methodologies such as relaxometry and imaging described in this chapter give precious information regarding morphology and texture of intact food samples.

N-Methyl-2-pyrrolidone (NMP) is a solvent with applications in different industrial fields. Although largely employed in aqueous mixtures, little is known on the structural and dynamic properties of this system. In order to improve the knowledge on NMP aqueous solutions, useful to the development of their applications, NMR spectroscopy, calorimetric titration, and puckering analysis of molecular dynamics (MD) simulations were employed in this work. Our calorimetric study evidenced the presence of strong interactions between NMP and water and revealed that, under comparable conditions, the solvation of NMP by water results in an interaction stronger than the solvation of water by NMP. Overall, the changes of H-1 and C-13 chemical shifts and 2D ROESY spectra upon dilution suggested a preferential location of water nearby the carbonyl group of NMP and the formation of hydrogen bonding between these two molecules. In parallel, observation of correlation times by C-13 NMR spectroscopy evidenced a different dynamic behavior moving from the NMP-rich region to the water-rich region, characterized by a maximum value at about 0.7 water mole fraction. MD simulations showed that the NMP conformation remains the same over the whole concentration range. Our results were discussed in terms of changes in the NMP assembling upon dilution., AuthorCount:6

A systematic study of a series of room-temperature ionic liquids, belonging to the alkylammonium nitrate family (XAN), was carried out at 298.15 K and 0.1 MPa with the aim of investigating the effect of the cationic chain length on some thermo-physical properties and their behavior in the organic solvent N-methyl-2-pyrrolidone (NMP), over the whole concentration range. Experimental densities were used to calculate molar volumes, V-m, and excess molar volumes, V-E. Complementary information was obtained by isothermal titration calorimetry that provided the values of the heat of mixing, H-E, and the excess partial molar enthalpies of each component, (H) over bar (E)(1) and (H) over bar (E)(2). The density values of neat XAN samples decreased as the alkyl chain length of the cation increases, whereas, the addition of the methoxy group to the considered smaller alkyl chain resulted in an increase of density. Negative V-E and H-E values were found for each XAN + NMP system, indicating the presence of strong attracting interactions between the constituents., AuthorCount:7