resumo
Thermochemical data of dibenzofuran, a compound of considerable industrial and environmental significance, obtained from experimental calorimetric and computational techniques are reported in this work. The enthalpy of fusion, (19.4 +/- 1.0) kJ mol(-1), at the temperature of fusion, (355.52 +/- 0.02) K, was determined by differential scanning calorimetry measurements of dibenzofuran. From the standard (p degrees = 0.1 MPa) molar enthalpies of formation of crystalline dibenzofuran, (-29.2 +/- 3.8) kJ mol(-1), and of sublimation, (84.5 +/- 1.0) kJ mol(-1), determined at T = 298.15 K by static bomb combustion calorimetry and by vacuum drop microcalorimetry, respectively, it was possible to calculate the enthalpy of formation of the gaseous compound, (55.0 +/- 3.9) kJ mol(-1), at the same temperature. The enthalpy of formation in the gaseous phase was also determined from G3(MP2)//B3LYP calculations. The same computational strategy was employed in the calculation of the standard molar enthalpies of formation, at T = 298.15 K, in the gas-phase, of single methylated derivatives of benzofuran and dibenzofuran.
palavras-chave
DIFFERENTIAL SCANNING CALORIMETERS; THERMODYNAMIC PROPERTIES; VAPOR-PRESSURES; O BOND; ENTHALPIES; SUBLIMATION; CALIBRATION; COMBUSTION; ENERGETICS; DENSITY
categoria
Chemistry; Crystallography
autores
Freitas, VLS; Gomes, JRB; da Silva, MDMCR
nossos autores
José R. B. Gomes
Investigador Principalagradecimentos
This work was mainly supported by Fundacao para a Ciencia e a Tecnologia (FCT), Lisbon, Portugal, and European Social Fund through strategic projects Pest-C/QUI/UI0081/2011 and Pest-C/CTM/LA0011/2011 awarded to CIQUP and CICECO, respectively. VLSF thanks FCT for Ph.D. research Grant SFRH/BD/41672/2007 and for the post-doctoral Grant SFRH/BPD/78552/2011. JRBG holds a Ciencia 2007 position of the Portuguese Ministry of Science.