Controlling factors determining addition and reduction products in the grignard reaction of substituted benzophenones, acetophenone and fluorenone with ‘EtMgBr’

Addition (Add.) vs reduction (Red.) products in the reactions of substituted benzophenones, acetophenone and fluorenone with ‘EtMgBr’ were compared in diethyl ether, 1,2‐dimethoxyethane and tetrahydrofuran. Plots of log (Add./Red.) vs σ‐values or the oxidation potentials of ketones showed characteristic upward curves depending on the polarity of the solvents. The results are discussed on the basis of both the combined effects of the stability of the monomeric radical ion pair and the dimeric radical ion pair derived from ketone and ‘EtMgBr’, and the well known Schlenk equilibrium of ‘EtMgBr’ in solutions.