An experimental system for measurement of enthalpies of sublimation by d.s.c.

Thermochemistry of benzoquinones

“…Therefore, the calculation of mass lost is necessary and was performed by independent experiments as has been previously described [26,27]. This set of experiments gave as result a lost mass for the p-benzoquinone of 2.38 AE 0.19% and for the duroquinone of 1.33 AE 0.21% in the procedure previous to the experiment of sublimation.…”

“…The calorimetric measurements of enthalpies of sublimation were performed using the isothermal mode operation of a modified DSC7 calorimeter [26,27]. The sensitive element of this device is a Perkin-Elmer DSC7 calorimetric holder assembly, within a vacuum chamber and connected to the DSC7 control device by an electrical feed.…”

“…For the duroquinone, the sublimation cells were completely opened standard pans for solids with a diameter of 6.5 mm. A working temperature of 298.15 K was established as the most recommendable from preliminary experiments [26].…”

Vapour pressures and enthalpies of vaporization of a series of the ferrocene derivatives

“…Cyclopentadienyl derivatives of iron and other transition metals are of the great significance for catalysis of C-C single bond coupling and cleavage reactions [1] or as combustion catalysts. Despite the fact that numerous iron cyclopentadienyl derivatives are known, thermodynamic studies [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] have focused on ferrocene only. This paper deals with determinations of the saturated vapour pressures of ferrocene, ferrocene-methanol, benzyl-ferrocene, and benzoyl-ferrocene.…”

Nonlinear models of the experimental thermal profile

“…In this field of study, it is typical to calculate vapor pressure from rate constant values using the Langmuir equation and then to fit the obtained values according to ClausiusClapeyron equation to determine standard enthalpy values, assuming that the enthalpy change (DH) is a thermodynamic property independent of the temperature; sometimes this approach works well for some ideal compounds and narrow ranges of temperature, but not for others, as Rojas-Aguilar et al [24], in which they reported several DH sub values for benzoic acid at different temperatures. Figures 2 and 3 show the different thermal profiles depending on the enthalpy function used.…”