EPR Spectroscopic Study of Radicals Formed from Aliphatic Carboxylic Esters and Related Compounds

• DOI: 10.1063/1.1696967
• Publication Date: 2005-01-09T08:01:39Z
• Authors: P. Smith; J. T. Pearson; P. B. Wood; T. C. Smith
• Keywords: Methyl acrylate; Ethyl acrylate; Hydrogen atom abstraction; Methyl acetate; Methyl group

A long-range coupling across the alkoxycarbonyl group of about 1.4–1.5 G has been observed in EPR spectra radicals formed hydroxyl-radical-initiated homopolymerization methyl acrylate, ethyl and methacrylate within an aqueous flow system at 25°±1°C. This further investigated by way a comprehensive study series simpler, related prepared under similar conditions from formate, acetate, propionate, isobutyrate hydrogen-atom abstraction with hydroxyl radicals. For ester other than those produced formates there was protons δ to unsaturated carbon atom when this adjacent oxycarbonyl group, i.e., for following functional structures, Ċ–CO–O–C C–CO–O–Ċ. The two yielded only HCOOĊH2 HCOOĊHCH3. These displayed γ formyl proton 2.4–2.5 G. All these results are shown be compatible simple model based on delocalized π-bond system. Comparison constants available data unsubstituted aliphatic suggests that value Qα McConnell equation aα=Qαρ is significantly lower conjugated radical nonconjugated radical. In support hydroxyl-radical attack esters, substrates formic, acetic, propionic, n-butyric, isobutyric acids methanol, ethanol, acetone have examined like fashion. Many esters underwent more one site. substrates, it possible estimate qualitatively selectivity relative intensities absorptions different reaction products. so obtained reckoned generally expected electrophilic character reactions.