The Nuclear Magnetic Resonance Spectra of Olefinic Protons and the Substituent Effects. III. Trans-forms of Methyl β-Substituted Acrylates, β-Substituted Vinyl Methyl Ketones and β-Substituted Acryloyl Chlorides

In the NMR absorption of the trans-forms of β-substituted acrylates, β-substituted vinyl methyl ketones and β-substituted acryloyl chlorides, the chemical shifts of protons situated at the cis-position to the substituents have been roughly determined by Hammett’s σp and Taft’s parameter, 0.40σI+0.70σR. From a comparison of the HA-shifts of the six olefinic systems (RCHA=CHBX, R=CH3, C6H5, H, CO2CH3, COCH3, COCl), these systems have been classified into two types—one, systems resembling the benzene derivatives, and the other, resembling the ethylene derivatives. Nevertheless, it has also been observed that the slope of each correlation line, on the whole, decreased in the order of the σ-value of the invariable substituent. The methyl proton shifts of β-substituted trans-acrylates, too, depend upon Hammett’s σp. The shifts of the proton (HB) at the β-positon can not be discussed from the viewpoint of Hammett’s substituent effect. However, they relate qualitatively with the electronegativity of the first atom of the substituent group.