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Phase transitions of 1,2-cyclohexanediol isomers studied by polarised light mic...
Leitão, Maria Luísa Planas; Castro, Ricardo A. E.; Costa, Felisbela S.; Redinha, J. S.Polarised light microscopy and DTA have been used to study the phase transitions observed in cis and trans-1,2-cyclohexanediol during heating/cooling cycles performed between ambient and melting temperatures to prove that the presence of impurities even in trace amounts can affect the thermal properties of the substances. Good quality commercial material before and after further purification were used in this s...
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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