13C Nuclear Magnetic Resonance Studies. XVI. 13C Spectra of some Substituted Acrylic Acids and their Methyl Esters. A Correlation of Olefinic Shieldings in α,β-unsaturated Carbonyl Systems

Abstract

The carbon-13 n.m.r. spectra of 26 α,β-unsaturated methyl esters and 16 substituted acrylic acids have been determined and the 13C shieldings are discussed. These data are compared with the recently reported values for several α,β-unsaturated carboxylic acids. Linear regression analysis of the olefinic shielding data for several α,β-unsaturated carbonyl derivatives yields a set of parameters which correlate the results with reasonable precision. The solvent dependence of the 13C shieldings of acrylic acid and methyl acrylate has been examined briefly. The proton results for the methyl esters are discussed briefly.