Publications

Abstract The mixed didodecyldimethylammonium bromide (DDAB)-sodium taurodeoxycholate (STDC)-(H2O)-H-2 catanionic system forms a large isotropic (L-1) phase at 25 degrees C. The evolution of microstructure along different dilution lines has been followed by means of rheology and NMR diffusometry. In general, the L, phase is characterised by a weak viscoelasticity and Newtonian response. In the STDC-rich regime (W-s = [DDAB]/[STDC] = 0.2), 5 wt% is an overlapping concentration at which the discrete-to-rodlike micellar transition occurs as indicated from the total surfactant concentration (C-s) dependency of both zero-shear viscosity (eta(0) similar to C-s(3.7)) and surfactant self-diffusion (D-s similar to C-s(-3.0)). As the surfactant molar ratio (W-s >= 1) increases, i.e., DDAB concentration increases, and at constant C-s, eta(0) decreases and D-s increases, indicating the formation of a multiconnected micellar network. (c) 2008 Elsevier Inc. All Fights reserved.

Abstract The first general methodology for the gram-scale preparation of previously overlooked beta-(hetero)aryl-alpha-nitro-alpha,beta-enals (3) is reported. Condensation of (hetero) aromatic aldehydes with 2-nitroethanol gave the E-isomers of uncommon beta-(hetero)aryl-alpha-hydroxymethyl-alpha,beta-unsatured-nitroalkenes (2), as determined by NOE and X-ray studies. alpha-Nitro-alpha,beta-enals 3 were subsequently obtained by hypervalent iodine oxidation of 2 as E-Z-mixtures in solid form. They showed varied stability and solvent-dependent thermal-promoted and photopromoted E-Z interconversion. Starting with furfural, experimental conditions were developed to prepare the corresponding nitroenal 3a enriched in either the E or the Z isomer: E-3a/Z-3a approximate to 90/10 and 20/80, respectively. In contrast with other structurally related compounds, nitroenals 3 have their (hetero)aryl-vinyl unit and their formyl and nitro groups all in a planar arrangement, both in solid form and in solution; accordingly, they are colored compounds with predicted high dipole moments. As deduced from solution-NMR and X-ray data, the C=C and the C=O double bonds in 3 are exclusively s-cis-oriented; this disposition corresponds in fact to the DFT-computed most stable conformer.

Abstract The solubility of water in tetradecyltrihexylphosphonium-based ionic liquids (ILs) with the bromide, bis(trifluoromethylsulfonyl)imide, bis(2,4,4-trimethylpentyl)phosphinate, chloride, decanoate, and dicyanimide anions was measured at temperatures between (288.15 and 318.15) K and atmospheric pressure. The effect of the nature of the IL anion, as well as the influence of temperature, are analyzed and discussed. From the experimental results, it was found that the anion-induced hydrophobicity increases from bis(2,4,4trimethylpentyl)phosphinate < decanoate < chloride < bromide < dicyanimide < bis(trifluoromethylsulfonyl)imide. COSMO-RS, a predictive method based on unimolecular quantum chemistry calculations, was used to predict the solubility of the water-IL binary systems. COSMO-RS was found to provide fine qualitative and quantitative predictions of the experimental data for extremely hydrophobic ILs. Less accurate predictions were observed with the increase of the anion hydrophilic character.

Abstract Vapor pressures of xanthene [CAS Registry No. 92-83-1] and phenoxathiin [CAS Registry No. 262-20-4] were measured in the temperature range from (318 to 382) K [(0.5 to 127) Pa] and from (318 to 373) K [(0.5 to 36) Pa], respectively, using a static method, in both crystalline and liquid phases. The vapor pressures of the crystalline phases of both compounds were also measured in the pressure range (0.1 to 1) Pa using the Knudsen effusion method. From the experimental results, the standard molar Gibbs energies and enthalpies of sublimation/vaporization, at T = 298.15 K, and the triple-point coordinates for these two compounds were derived. The enthalpies and temperatures of fusion were also determined using differential scanning calorimetry. To the best of our knowledge, vapor pressure data reported here are the first for crystalline phenoxathiin and for liquid xanthene.

Abstract Numerical parameters of the molecular networks, also referred as Topological Indices or Connectivity Indices (CIs), have been used in Bioorganic and Medicinal Chemistry to find Quantitative Structure-Activity, Property or Toxicity Relationship (QSAR, QSPR and QSTR) models. QSPR models generally use CIs as inputs to predict the biological activity of compounds. However, the literature does not evidence a great effort to find QSAR-like models for other biologically and chemically relevant systems. For instance, blood proteome constitutes a protein-rich information reservoir, since the serum proteome Mass Spectra (MS) represents a potential information source for the early detection of Biomarkers for diseases and/or drug-induced toxicities. The concept of mass spectrum network (MS network) for a single protein is already well-known. However, there are no reported results on the use of CIs for a MS network of a whole proteome to explore MS patterns. In this work, we introduced for the first time a novel network representation and the CIs for the MS of blood proteome samples. The new network bases on Randic's Spiral network have been previously introduced for protein sequences. The new MS CIs, called here Spiral Markov Connectivity (SMCk) of the MS Spiral graph can be calculated with the software MARCH-INSIDE, combining network and Markov model theory. The SMCk values could be used to seek QSAR-like models, called in this work Quantitative Proteome-Property Relationships (QPPRs). We calculate the SMCk values for 62 blood samples and fit a QPPR model by discriminating proteome MS, typical of individuals susceptible to suffer drug-induced cardiotoxicity from control samples. The accuracy, sensitivity, and specificity values of the QPPR model were between 73.08% and 87.5% in training and validation series. This work points to QPPR models as a powerful tool for MS detection of biomarkers in proteomics.

Abstract The standard (p(o)=0.1 MPa) molar enthalpies of formation, in the gaseous phase, at T=298.15 K, for 2,5-dimethylpyrazine (2,5-DMePz) and for the two dimethylpyrazine-N,N'-dioxide derivatives, 2,3-dimethylpyrazine-1,4-dioxide (2,3-DMePzDO) and 2,5-dimethyl-pyrazine-1,4-dioxide (2,5-DMcPzDO), were derived from the measurements of standard massic energies of combustion, using a static bomb calorimeter, and from the standard molar enthalpies of vaporization or sublimation, measured by Calvet microcalorimetry. The mean values for the molar dissociation enthalpy of the nitrogen-oxygen bonds, < DHmo >(N-O), were derived for both N,N'-dioxide compounds. These values are discussed in terms of the molecular structure of the two N,N'-dioxide derivatives and compared with < DHmo >(N-O) values previously obtained for other N-oxide derivatives.

Abstract Ionic liquids (ILs) have recently garnered increased attention because of their potential environmental benefits as "green" replacements over conventional volatile organic solvents. While ILs cannot significantly volatilize and contribute to air pollution, even the most hydrophobic ones present some miscibility with water posing environmental risks to the aquatic ecosystems. Thus, the knowledge of ILs toxicity and their water solubility must be assessed before an accurate judgment of their environmental benefits and prior to their industrial applications. In this work, the mutual solubilities for [C(2)-C(8)mim][Tf(2)N] (n-alkyl-3-methylimidazolium bis-(trifluoromethylsulfonyl)imide) and water between 288.15 and 318.15 K at atmospheric pressure were measured. Although these are among the most hydrophobic ionic liquids known, the solubility of water in these compounds is surprisingly large, ranging from 0.17 to 0.36 in mole fraction, while the solubility of these ILs in water is much lower ranging from 3.2 x 10(-5) to 1.1 X 10(-3) in mole fraction, in the temperature and pressure conditions studied. From the experimental data, the molar thermodynamic functions of solution and solvation such as Gibbs energy, enthalpy, and entropy at infinite dilution were estimated, showing that the solubility of these ILs in water is entropically driven. The predictive capability of COSMO-RS, a model based on unimolecular quantum chemistry calculations, was evaluated for the description of the binary systems investigated providing an acceptable agreement between the model predictions and the experimental data both with the temperature dependence and with the ILs structural variations.

Abstract Thermophysical and thermochemical studies have been carried out for crystalline parabanic acid. The thermophysical study was made by differential scanning calorimetry, DSC, over the temperature interval between T = (263 and 473) K. Two phase transitions were found: at T = (392.3 +/- 1.6) K with the enthalpy of transition of (2.1 +/- 0.4) kJ . mol(-1) and at T = (509.8 +/- 1.5) K, when the compound was scanned to its fusion temperature. The standard (p degrees = 0.1 MPa) molar enthalpy of formation, at T = 298.15 K, for crystalline parabanic acid was determined using static-bomb combustion calorimetry as -(590.2 +/- 1.0) kJ . mol(-1). The standard molar enthalpy of sublimation, at T = 298.15 K, was derived from the variation of their vapour pressures, measured by the Knudsen-effusion method, with the temperature. These two thermochemical parameters yielded the standard molar enthalpy of formation in the gaseous phase, at T = 298.15 K, as -(470.8 +/- 1.2) kJ . mol(-1).

Abstract A series of newly hydrophobically modified polymers (dexC(16)) with different degrees of substitution (DSC16) have been synthesized. They can self-assemble to form micelle-like aggregates through association of the hydrophobic alkyl chains in aqueous solution. The self-aggregation processes, i.e. the critical micelle concentrations (cmc's) of the polymers were characterized by steady-state fluorescence. Further, the interaction between these dexC(16) polymers and ionic surfactants (SOS, SDS and DTAC) was investigated by isothermal titration calorimetry (ITC). For the studied mixed systems some important parameters can be derived from calorimetric titration curves, such as interaction enthalpies, critical concentrations and enthalpies of aggregation. The critical concentrations and the aggregation behaviour for the dexC(16)/SDS system were confirmed by fluorescence measurements. The effects of hydrophobic side group concentrations on the interaction were evaluated in detail. Importantly, we show that the aggregation behaviour of the mixed systems depends on the molar ratio of surfactant to hydrophobic side group (R=n(s)/n(side) (group)).