The S-C-O (O-C-S) Edward-Lemieux effect is controlled by a p-orbital on oxygen. Evidence from electron momentum spectroscopy, photoelectron spectroscopy, X-ray crystallography, and density functional theory

The nature of the lone pairs in the series of molecules methyl propyl sulfide, dimethylthiomethane, methyl thiomethyl ether (MTME), dimethoxy methane, and methyl propyl ether has been examined experimentally by the techniques of electron momentum spectroscopy and photoelectron spectroscopy. Although the HOMO of MTME is found to be a p-orbital on sulfur, it is the p-orbital on oxygen that controls the Edward-Lemieux effect (the anomeric effect) in this molecule through a combination of both stabilizing and destabilizing interactions with C-S orbitals.