Thermodynamic study of sesamol, piperonyl alcohol, piperonylic acid and homopiperonylic acid: A combined experimental and theoretical investigation

M. Agostinha R. Matos*, Manuel J.S. Monte, Clara C.S. Sousa, Ana R.R.P. Almeida, Victor M.F. Morais

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)

Abstract

The standard (p° = 0.1 MPa) molar energies of combustion in oxygen, at T = 298.15 K, of four 1,3-benzodioxole derivatives (sesamol, piperonyl alcohol, piperonylic acid and homopiperonylic acid) were measured by static bomb calorimetry. The values of the standard molar enthalpies of sublimation, at T = 298.15 K, were derived from vapour pressure-temperature measurements using the Knudsen effusion technique. Combining these results the standard molar enthalpies of formation of the compounds, in the gas phase, at T = 298.15 K, have been calculated: sesamol (-325.7 ± 1.9) kJ mol-1; piperonyl alcohol (-329.0 ± 2.0) kJ mol-1; piperonylic acid (-528.9 ± 2.6) kJ mol-1 and homopiperonylic acid (-544.5 ± 2.9) kJ mol-1. The most stable geometries of all the compounds were obtained using the density functional theory with the B3LYP functional and two basis sets: 6-31G** and 6-311G**. The nonplanariry of the molecules was analyzed in terms of the anomeric effect, which is believed to arise from the interaction between a nonbonded oxygen p orbital and the empty orbital σ*co involving the other oxygen atom. Calculations were performed to obtain estimates of the enthalpies of formation of all the benzodioxoles using appropriate isodesmic reactions. There is a perfect agreement between theoretical and experimental results.

Original languageEnglish
Pages (from-to)908-914
Number of pages7
JournalOrganic and Biomolecular Chemistry
Volume2
Issue number6
DOIs
Publication statusPublished - 21 Mar 2004

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