文摘
The rotameric conformations of the phenyl ring in both the axial and the equatorial conformers of phenyl substituted 1,3-dioxanes and tetrahydropyrans are compared with those of the corresponding phenylcyclohexanes at the MP2/6-311+G* level. The compounds with an axial phenyl commonly adopt a conformation in which the plane of the aromatic ring is perpendicular to the benzylic C鈥揌 bond. However, axial 5-phenyl-1,3-dioxane adopts a 鈥減arallel鈥?conformation that allows an ortho hydrogen to be proximate to the two ring oxygens, leading to attractive CH路路路O interactions. Stabilizing Coulombic interactions of this sort are found with many of the oxygen-containing six-membered rings that were investigated.