An Ab Initio Molecular Orbital Theory Study of the Conformational Free Energies of 2-Methyl-, 3-Methyl-, and 4-Methyltetrahydro-2H-Pyran
Ab initio molecular orbital theory with the 6-31G(d), 6-31+G(d), 6-31G(d,p), 6-311G(d,p), 6-311+G(d,p), 6-31G(2d), 6-311G(2d), and 6-311G(2d,p) basis sets have been used to calculate the conformational enthalpies (ΔH°), entropies (ΔS°), and free energies (ΔG°) of the axial and equatorial conformers of 2-methyl-, 3-methyl-, and 4-methyltetrahydro-2H-pyran (tetrahydropyran, oxacyclohexane, oxane) and methylcyclohexane (toluene). Although HF and MP2 generally gave higher conformational free energies (ΔG°) than the experimentally reported values, other MP2 calculations gave ΔG° values in excellent agreement with experimental results for methylcyclohexane [6-311G(d 311G(d,p)] and 3-methyltetrahydro-2H-pyran [6-31+G(d), 6-311+G(d,p)]. Consistent with solution studies, the MP2 calculations gave larger ΔG° values for 4-methyltetrahydro-2H-pyran than for methylcyclohexane.
MSU Digital Commons Citation
Freeman, Fillmore; Kasner, Marc; and Hehre, Warren J., "An Ab Initio Molecular Orbital Theory Study of the Conformational Free Energies of 2-Methyl-, 3-Methyl-, and 4-Methyltetrahydro-2H-Pyran" (2001). Department of Chemistry and Biochemistry Faculty Scholarship and Creative Works. 64.