Thermochemical and structural studies of gallic and ellagic acids

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Dávalos J.Z.
Lima C.F.R.A.C.
Santos L.M.N.B.F.
Romero V.L.
Liebman J.F.
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We report a study on the energetics and structural properties of gallic (1) and ellagic (2) acids. The experimental values of standard enthalpy of formation in solid state at 298.15 K, (cd) of 1 as (−985.0 ± 2.9 kJ·mol−1) and 2 as (−1377.9 ± 4.7 kJ·mol−1) have been determined. The vapour pressure of 1 have been measure by Knudsen effusion methodology and the derived enthalpy of sublimation, , was combined with the (cd) in order to derive its gas-phase enthalpy of formation, (1,g) = −835.7 ± 4.0 kJ·mol−1. Quantum chemical calculations, at DFT (M05-2X) and composite ab initio Gn (n = 3, 4) levels of theory, provided the consistency of the experimental results and a plausible estimation of (g) of 2 as (−1128.6 ± 6.4 kJ·mol−1), which was deduced from the isodesmic-reactions methodology.
J.Z.D acknowledges the support funding to IQFR-CSIC (Spain) and peruvian CONCYTEC (INNÓVATE PERÚ, ECIP-1-P-030-14 Grant).
Palabras clave
Knudsen effusion, Gallic-ellagic acids, Combustion calorimetry, Enthalpy of formation