Vinyl cations. Part 13. Secondary kinetic deuterium isotope effects in the solvolysis of ring-substituted β-styryl trifluoromethanesulphonates

Abstract

The β-kinetic deuterium isotope effects have been measured in the solvolysis of a series of ring-substituted β-styryl trifluoromethanesulphonates. At 75 °C in aqueous 80% ethanol for the parent compound, k_H/k_D= 1.45; for p-Cl, k_H/k_D= 1.74; for m-Cl, k_H/k_D= 1.61; for p-CF₃, k_H/k_D= 1.64; for p-NO₂, k_H/k_D= 1.71. Both the protio- and deuterio-series gave an excellent Hammett correlation with σ⁺(ρ–4.12 and –4.17, respectively). The products of solvolysis were the corresponding acetophenones and phenylacetylenes. The significance of these results is discussed.