The rate constants for the iodination of acetophenones have been measured for various mono and disubstituted acetophenones by conductance method in 20% aqueous pyridine. Linear plots were obtained by plotting the logarithms of the specific reaction rate (log k) against the logarithms of the dissociation constant (log K) and the dipole moment (µ) against energy of activation (E). From the slope of the regres­sion line fitted to log k and \(\sigma\)00 data for na-substituted compounds, the value of ' p' the reaction constant has been calculated at various temperatures. The effective sigma values (\(_\sigma^-\)) and resonance interaction energy (Δ,Δ.Fp) for various substituents have been determined and the results thus obtained are discussed.