Session: Physical Chemistry Poster:

In previous spectroscopic studies of 1,3-dioxole [JACS, 1993, 115, 12132-12136] and 1,3-benzodioxole [JACS, 1999, 121, 5056-5062] we demonstrated that the analysis of the ring-puckering potential energy function (PEF) of a “pseudo-four-membered ring” molecule makes it possible to assess the magnitude of the anomeric effect for molecules with O-C-O linkages. In the present study we have utilized high level theoretical computations to calculate the PEFs for 1,3-dioxole and 1,3-benzodioxole and ten related molecules containing sulfur and selenium atoms and possessing the anomeric effect. The potential energy parameters derived for the PEFs directly provide a comparison of the relative magnitudes of the anomeric effect for molecules possessing O-C-O, O-C-S, O-C-Se, S-C-S, S-C-Se, and Se-C-Se linkages. The torsional potential energies produced by the anomeric effect for these linkages were estimated to range from 5.97 kcal/mole for O-C-O linkages down to 1.91 kcal/mole for Se-C-Se linkages. The calculations also yielded the structural parameters, barriers to planarity, and ring-puckering angles for each of the twelve molecules studied. Improved PEFs for 1,3-dioxole and 1,3-benzodioxole were also calculated. The calculations also support the conclusion that the relatively low barrier to planarity of 1,3-benzodioxole results from competitive interactions between its benzene ring and the oxygen atom p orbitals. The anomeric effect is illustrated below.

Esther Juliana Ocola

Postdoctoral Research Associate, Texas A&amp;M University, College Station

Appearances

Postdoctoral Research Associate, Texas A&M University, College Station