Enhancement of the Electrophilic Character of Vinyl Monomers by Complexation with Zinc Bromide as Measured by NMR

The extent of electron withdrawal in electron-poor monomers acrylonitrile and methyl acrylate caused by the addition of zinc bromide was measured by NMR. Zinc bromide complexation caused significant downfield shifts with acrylonitrile and methyl acrylate. Electron-rich monomer vinyl acetate showed much smaller downfield shifts upon complexation with zinc bromide. These NMR data give for the first time a quantitative assessment of the extent to which complexation to zinc bromide enhances the electrophilic character of vinyl monomers.