Energetic studies of two oxygen heterocyclic compounds Xanthone and tetrahydro-γ-pyrone
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The present work reports an experimental thermochemical study supported by state of the art calculations of two heterocyclic compounds containing oxygen in the ring: xanthone and tetrahydro-γ-pyrone. The standard (pº = 0.1 MPa) molar enthalpies of formation in the condensed phase, at T = 298.15 K, were derived from the measurements of the standard molar energies of combustion in oxygen atmosphere, using a static bomb calorimeter. The standard molar enthalpies of sublimation or vaporization, at T = 298.15 K, of the title compounds were obtained from Calvet microcalorimetry measurements. These values were used to derive the standard enthalpies of formation of the compounds in the gas-phase at the same temperature, which were compared with estimated data from G3(MP2)//B3LYP computations.
KeywordsCalvet microcalorimetry Combustion calorimetry Enthalpy of formation Enthalpies of transition G3(MP2)//B3LYP calculations Heat capacities
Thanks are due to Fundação Para a Ciência e Tecnologia (FCT), Lisbon, Portugal, for financial support to Centro de Investigação em Química - UP and to CICECO. V. L. S. Freitas thanks FCT and European Social Fund for the award of a Ph.D. Research Grant SFRH/BD/41672/2007.
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