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Infrared study of the acidic and basic forms of betaxolol
Canotilho, João; Castro, R. A. Esteves de; Helena, M.; Teixeira, S. F.; Leitão, M. Luísa P.; Redinha, J. SimõesBetaxolol and its respective hydrochloride salt were studied in solution by computational calculations and infrared spectroscopy. The solution molecular conformations were taken to be the same as those exhibited by the compounds in the solid state given by X-ray diffraction and calculated after full geometry optimization by ab initio Hartree-Fock methods using the 6-31G(d) basis set. Infrared spectra of carbon ...
Conformational study of erythritol and threitol in the gas state by density fun...
Jesus, António J. Lopes; Tomé, Luciana I. N.; Rosado, Mário Túlio S.; Leitão, M. Luísa P.; Redinha, José S.Density functional theory calculations using the B3LYP functional and the 6-311++G(d,p) basis set were carried out on the isolated molecules of erythritol and L-threitol. For the meso isomer, a relatively large number of conformers have to be considered to describe the gas state structure. The lowest energy conformer is characterized by the establishment of a strong intramolecular H-bond between the two termina...
Polymorphism of pindolol, 1-(1H-indol-4-yloxyl)-3-isopropylamino-propan-2-ol
Nunes, Sandra C. C.; Eusébio, M. Ermelinda; Leitão, M. Luísa P.; Redinha, J. S.Crystallization of pindolol from the melt was studied by differential scanning calorimetry (DSC) and polarized light thermomicroscopy (PLTM) in order to discriminate the polymorphic forms obtained by this method. The crystallization process originates one exothermic signal localized in two different well-defined temperature ranges. Fusion gives rise to overlapped curves, which were analysed by peak-fitting. The...
Effect of solvent and temperature on solution-crystallized terfenadine
Leitão, M. Luísa P.; Canotilho, João; Ferreira, Simone C. R.; Sousa, Adriano T.; Redinha, J. SimõesThe aim of this work was to understand the crystallization process of terfenadine in solution. ; http://www.sciencedirect.com/science/article/B6THV-49SWCDJ-1/1/bfcb0feff088fbe244525634b1e2dfda
Enthalpy of vaporisation of butanediol isomers
Eusébio, M. Ermelinda; Jesus, A. J. Lopes; Cruz, Mafalda S. C.; Leitão, M. Luísa P.; Redinha, J. SimõesThe enthalpies of vaporisation of isomers of butanediol were determined by calorimetric measurements. A Knudsen effusion cell was used for this purpose. ; http://www.sciencedirect.com/science/article/B6WHM-47K2P6J-2/1/6a970623f372c267e60917eff9f702c6
Molecular Structure of Butanediol Isomers in Gas and Liquid States: Combinatio...
Jesus, A. J. Lopes; Rosado, Mário T. S.; Leitão, M. Luísa P.; Redinha, José S.Density functional theory (Becke3LYP/6-311++G**) conformational analysis was carried out for all positional butanediol isomers. Taking into account the relative populations of the most stable conformers at 298.15 K, the weighted mean enthalpies of each butanediol isomer in the gas state were computed. Combining these results with the experimental values for the enthalpies of vaporization at 298.15 K, an estimat...
On the interpretation of the enthalpy of solvation of hydroxyl cyclohexane deri...
Costa, Felisbela S.; Eusébio, M. Ermelinda; Redinha, J. S.; Leitão, M. Luísa P.Scaled particle theory was used for calculating the enthalpy of cavity formation in the solvation process of hydroxyl cyclohexane derivatives in water and in organic solvents. From the values calculated for the enthalpy of formation of the cavity and from those quoted for the enthalpy of solvation, the enthalpy of solute/solvent interaction was determined. This thermodynamic property shows that the formation of...
Enthalpy of solution of terfenadine in ethanol/water mixtures
Canotilho, João; Costa, Felisbela S.; Sousa, Adriano T.; Redinha, J. Simões; Leitão, M. Luísa P.The enthalpy of solution of terfenadine in ethanol/water mixtures, 0-20.5 wt.% of water was determined by calorimetry. A Sudden increase of 1-2 kJ mol-1 in the enthalpy at a concentration value around 0.01 mol kg-1 is observed. This step in the enthalpy is interpreted as due to solute n-mer aggregates formation. The solubility of terfenadine in the cosolvent systems used in the calorimetric studies was determin...
Enthalpies of solvation of hydroxyl cyclohexane derivatives in different solvents
Costa, Felisbela S.; Eusébio, M. Ermelinda; Redinha, J. S.; Leitão, M. Luísa P.The enthalpies of solution of cyclohexanol, cis -1,2-cyclohexanediol, and myo -inositol in water, formamide, and dimethylsulphoxide at T = 298.15 K as well as their enthalpies of vaporization or sublimation were determined. The enthalpies of solvation were calculated from the data obtained. The contributions of the polar and non-polar groups to the behaviour of the solute molecules in polar solvents are analys...
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