Substituent Effects on the Activation Parameters for the Methoxymercuration of p-Substituted Styrenes

Article abstract of DOI:10.1021/jo00322a002

The activation parameters for the methoxymercuration of a series of p-substituted styrenes in anhydrous methanol have been determined.The values of ΔH(excit.) and ΔS(excit.) are consistent with the formation of bridged activated complexes in the rate-determining step of these reactions.Analysis of the substituent effects on the values of δ ΔG(excit.) for these reactions using the Yukawa-Tsuno equation required the use of small values for the r parameter.This finding is also consistent with the formation of bridged activated complexes in the rate-determining step.Variations of the substituents have small effects on ΔH(excit.) but large effects on ΔS(excit.). δ ΔH(excit.) is not linearly related to either δ ΔS(excit.) or δ ΔG(excit.).However, δ ΔG(excit.) - as expected for a reaction series in which the values of δ ΔH(excit.) are small and/or constant - is a linear function of δ ΔS(excit.).Product studies on styrene and its p-MeO and p-NO2 derivatives show that these reactions are clean and that they occur regiospecifically, giving the expected Markovnikov addition product in each case.