M. Luísa P. Leitão

Enthalpy of vaporisation of butanediol isomers

Abstract The enthalpies of vaporisation of isomers of butanediol were determined by calorimetric measurements. A Knudsen effusion cell was used for this purpose. The values of the standard enthalpy of vaporisation obtained for the different isomers were compared and significant differences were found between them.

A calorimetric study of phase transitions for some cyclohexanediols

Phase transitions in solid cis-1,2-cyclohexanediol and trans-1,2-cyclohexanediol and cis/trans-1,4-cyclohexanediol have been studied by differential scanning calorimetry over the temperature range 241 to 383 K. Besides a low-temperature crystalline form, DSC curves show the existence of a solid rotator phase in cis-1,2-cyclohexanediol whilst for the others, only one solid phase is present. Enthalpies of sublimation and vaporization were determined by evaporation into a vacuum using an isothermal calorimeter.

Calorimetric study of polymorphic forms of terfenadine

Abstract Terfenadine polymorphic forms have been prepared by crystallization from ethanol and methanol solutions. The two polymorphs were studied by differential scanning calorimetry (DSC) and thermogravimetry (TG) in a temperature range between 233 and 443 K. From DSC data, structural differences between both forms were pointed out. Enthalpies for solution processes of the polymorphs in ethanol and in methanol were determined. Differences between both solid forms as well as between the solvent behaviour are well noted from the standard solution enthalpy values and from the variation of the enthalpy with concentration.