Abstract
Abstract Rates of reactions of MeMgBr and MeLi with substituted benzophenones (BPs) were determined by using a stopped-flow method. The Hammett plots for the reactions of MeMgBr in THF and in Et2O at 0 °C gave ρ values of 0.99 ± 0.09 and 0.99 ± 0.08, respectively; such values were in excellent agreement with the ρ value determined previously by competition experiments in THF. The Hammett ρ value (0.40 ± 0.07) for the reaction of MeLi in Et2O at 0 °C also agreed with that determined by competition experiments within experimental errors. A logarithmic plot of the rate constant vs the reagent concentration for the reaction of BP and MeMgBr in THF gave a linear plot with a slope of close to unity, whereas that in Et2O showed saturation at a higher MeMgBr concentration, reflecting different aggregation states in different solvents. An analogous plot for MeLi in Et2O gave a curved logarithmic plot with a slope of 1/4 at a higher reagent concentration and a slope of 1/2 at a lower reagent concentration range, suggesting that the aggregation of MeLi is concentration dependent.
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