13C N.M.R. STUDIES: PART V. CARBON-13 SPECTRA OF SOME SUBSTITUTED STYRENES

Abstract

The 15.1 Mc/s 13C n.m.r. spectra of 23 substituted styrenes have been examined and the shieldings of the various carbon nuclei determined. Several meta- and para-substituted derivatives were included to study the effects of polar substituents on the vinyl carbon chemical shifts. In agreement with previous proposals, a linear correlation with the Hammett σ parameter is found for the β-carbon shieldings, but not for those of the α-carbons. Nine ortho-substituted examples and two α-substituted compounds were investigated to compare their chemical shifts with results for related carbonyl compounds. While the 13C data exhibit marked differences in the hindered compounds, the variations differ from those observed in the more polar carbonyl systems.