Conformational behaviors of ۲-m ethyl-۱,۳,۲-dioxaphosphorin ane. Ahy brid density func tional theory study and natural bond orbital interpretatio n

The stabilities of the conformations of the saturated heterocyclic compounds cannot be explained solely by steric f actors. Stere oelctronic effects hav e significant impacts on the confo rmations an d configurations of saturated heterocyclic compounds . The pre ferred geom etry of the saturated heterocyclic compounds can be v iewed as theresult of the maxim ization of a n interaction between t he best dono r lone pair and the best acceptor bond.۱-۳ The m ost dominant conforma tion-contro lling factor in carbohydrate compo unds is kno wn as the an omeric effect (AE).۴ T he AE is in favor of th e axial conformation of a six-membered saturated ring in opposition to the steric effect which normally leads to a p reference f or the equato rial confor mation. Although the im portance of the hyperconjugative interactions in six membered phosph orinane heterocycles h as investigated,۵,۶ there is no published experim ental or quantitative theoretical data about the donor-acceptor d elocalization effects o n theconfo rmational properties of ۲-methyl-۱,۳,۲-dio xaphosphorinane. In this work, the contributions of the total dipole moments, steric effects and the AE associated with theelectr on delocaliz ation on th e conforma tional and structural p roperties of ۲-methyl-۱,۳,۲- dioxa phosphorinane were i nvestigated by means of hybrid density functional theory (B۳L YP/۶-۳۱۱+G**) based m ethod and natural bond orbital (NBO) interpret ation.۷,۸