Relative thermodynamic stabilities of the isomeric dihydrofurans and isomeric dihydropyrans. An experimental and DFT study |
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Authors: | Esko Taskinen Teija Alanko Joel F. Liebman |
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Affiliation: | (1) Department of Chemistry, University of Turku, FIN-20014 Turku, Finland;(2) Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, Baltimore, MD 21250,, USA |
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Abstract: | The relative thermodynamic stabilities of 2,5-dihydrofuran (1) and 2,3-dihydrofuran (2), and of 3,4-dihydro-6H-pyran (3) and 3,4-dihydro-2H-pyran (4), were determined at several temperatures by base-catalyzed equilibration in DMSO solution. For 1 → 2, = –15.4±0.1 kJ mol−1, =–12.6±0.5 kJ mol−1, and =9.5±1.3 J K−1 mol−1 at 298.15 K. The second-law reaction enthalpy agrees with literature data based on calorimetric enthalpies of hydrogenation of the isomeric forms in hexane. For 3 → 4, =–19.3±0.2 kJ mol−1, = –18.9±1.1 kJ mol−1 and =1.1±3.0 J K−1 mol−1 at 298.15 K: the experimental reaction enthalpy is in marked disagreement with literature data based on estimation. On the other hand, both of the experimental reaction enthalpies of the present study are in good agreement with DFT calculations using the B3LYP functional and 6-311+G(2d,p) basis set. |
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Keywords: | Dihydrofurans Dihydropyrans Thermodynamic stability Reaction enthalpy Reaction entropy DFT calculations |
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