Linear free energy relationship for the anomeric effect: MP2, DFT and ab initio study of 2-substituted-1,4-dioxanes |
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Authors: | Dabbagh Hossein A Naderi Marzie Chermahini Alireza Najafi |
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Institution: | aDepartment of Chemistry, Isfahan University of Technology, 8415483111 Isfahan, Iran;bDepartment of Chemistry, Faculty of Science, Yasouj University, Yasouj, Iran |
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Abstract: | The anomeric effect of 2-substituted 1,4-dioxane derivatives was calculated and compared with the values for substituted cyclohexane. The bond lengths, bond angles, torsion angles, and relative energies of axial and equatorial conformers of 2-substituted 1,4-dioxanes were calculated by the second-order Møller–Plesset (MP2), density functional theory (DFT/B3LYP), and Hartree–Fock (HF) methods using 6-31G∗ basis set. The energy differences between the axial and equatorial conformers, endo and exo-anomeric effects, repulsive non-bond and H-bonding interactions were investigated. A linear free energy relationship (LFER) between calculated (MP2/6-31G∗) anomeric effect and inductive substituent constants (σI) was obtained for 2-substituted-1,4-dioxanes (slope = 6.19 and r2 = 0.967). The calculated energy differences indicate lower equatorial orientation for 2-substituted-1,4-dioxanes compared to the 2-substituted-tetrahydropyrans. The contribution of resonance, hyperconjugation, inductive, steric, hydrogen bonding, electrostatic interaction, and level of theory influences the anomeric effect. |
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Keywords: | Anomeric effect Hyperconjugation 1 4-Dioxanes LFER MP2 DFT |
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