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

• Type: Article in International Scientific Journal
• Date: 2004

Authors

Matos, MAR (Author) FCUP; Monte, MJS (Author) FCUP; Sousa, CCS (Author) FCUP; Almeida, ARRP (Author) Other; Morais, VMF (Author) ICBAS

Journal

Title: Organic and Biomolecular Chemistry

Vol. 2

Pages: 908-914

ISSN: 1477-0520

Publisher: Royal Society of Chemistry

Indexing

ISI Web of Knowledge - 16 Citations

Scopus - 19 Citations

Scientific classification

FOS: Natural sciences > Chemical sciences

Other information

Authenticus ID: P-000-DB0

DOI: 10.1039/b400107a

Abstract (EN): The standard (p(o) = 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 nonplanarity 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 sigma*(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.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 7