Transmission of Substituent Effects through Oxygen and Sulfur Atoms. I. 1H Chemical Shifts of Ring-substituted Phenyl Vinyl Ethers and Sulfides

The proton chemical shifts of the vinyl group in ring-substituted phenyl vinyl ethers (PVE) and sulfides (PVS) were measured and related to the Hammett σ constants. It was found that the ρ value for the β-trans proton of PVS, −0.448 τ⁄σ, is greater in magnitude than that of PVE, −0.378 τ⁄σ, in contrast to the tendency reported for the methyl hydrogens in anisole and thioanisole. The results can best be explained in terms of the concept of the through-conjugative (pπ-dπ-pπ) behavior of the sulfur atom interposed between two unsaturated groups.