Hybrid-DFT Study and NBO Analysis of the Stereoelectronic Interaction Effects (Associated with the Anomeric Effects) on the Conformational Properties of 2,3,5,6-Tetrahalo-1,4-dioxanes and Their Analogs Containing S and Se Atoms

摘要

NBO analysis and hybrid density functional theory-based method (B3LYP/6-311+G**) was used to study the anomeric effects (AE), dipole-dipole interactions, and steric repulsion effects on the conformational properties of 2,3,5,6-tetrahalo-1,4-dioxane [halo = F (1), Cl (2), Br (3)], 2,3,5,6-tetrahalo-1,4-dithiane [halo = F (4), Cl (5), Br (6)], and 2,3,5,6-etrahalo-1,4-diselenane [halo = F (7), Cl (8), Br (9)]. B3LYP/6-311+G** results revealed a strong axial preference in compounds 1-3. Gibbs free energy difference (G _eq-G _ax) values (e.g., ΔG _eq-ax) between the axial and equatorial conformations of compound 1 to compound 3 are 8.19, 3.86, and 3.13 kcal mol−1, respectively, as calculated by the B3LYP/6-311+G** level of theory. On the other hand, the NBO analysis of donor-acceptor (bond-antibond) interactions revealed that the AE for compounds 1-3 are −12.26, −16.46, and −18.11 kcal mol−1, respectively. Contrary to the increase of the AE values from compound 1 to compound 3, the increase of the steric repulsions (e.g., 1,3-syn-axial repulsions) could fairly explain the decrease of the axial conformation stability in compounds 1-3 compared to their equatorial conformations. Further, the correlations between the AE, structural parameters, and conformational behavior of compounds 4-9 have been investigated.View full textDownload full textKeywordsAb initio, anomeric effects, molecular modeling, NBO; 2,3,5,6-tetrahalo-[1,4]dioxane, 2,3,5,6-tetrahalo-[1,4]diselenane, 2,3,5,6-tetrahalo-[1,4]dithianeRelated var addthis_config = { ui_cobrand: "Taylor & Francis Online", services_compact: "citeulike,netvibes,twitter,technorati,delicious,linkedin,facebook,stumbleupon,digg,google,more", pubid: "ra-4dff56cd6bb1830b" }; Add to shortlist Link Permalink http://dx.doi.org/10.1080/10426500903530875