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

Abstract

The 15.1 Mc/s 13 C 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 13 C data exhibit marked differences in the hindered compounds, the variations differ from those observed in the more polar carbonyl systems.