Kinetic isotope effects. Part 7.—Ionization of (d)-phenylmethylacetophenone
Abstract
Measurements are reported on the hydroxide-catalyzed ionization of (d)-phenylmethylacetophenone in the presence of varying amounts of dimethyl sulphoxide. The kinetic hydrogen isotope effect (kH/kT) increases with increasing basicity until at a H– value of 16.5 it reaches a maximum. The value of the Brönsted exponent β is 0.49 ± 0.02 for both isotopes. For several media, activation energies and pre-exponential factors have been determined. The difference ET–EH reaches a maximum at a H– value of 16.8. The ratios of AH/AT reflect the importance of solvent reorganization contributions.