OXIDATION OF SUBSTITUTED STYRENES BY THALLIUM TRIACETATE

The products and kinetics of the oxidation of six ring-substituted styrenes by thallium triacetate in acetic acid have been determined. Two products, l-aryl-1,2-ethanediol diacetate and 2-aryl-1,1-ethanediol diacetate, are obtained, with the latter predominating as the electron-donating ability of the ring substituent increases. A correlation of the logarithm of the product ratio with Brown σ+ values has been found with p+ = -1.7. 1- Deuteriostyrene yields 1-deuterio-1-phenyl-1,2-ethanediol diacetate and 1-deuterio-2-phenyl-1,1-ethanediol diacetate. The rate of oxythallation of styrenes is second order, first order in each reactant. A Hammett-type correlation with Brown σ+ values has been established with p+ = -2.2. The activation parameters ΔH‡ = 7.9 kcal/mol and ΔS‡ = -41 cal/deg for the reaction of p-methylstyrene have been evaluated from rate data at 19.7, 50.1, and 75.0°. The activated complex for oxythallation has approximately the same carbonium ion character as for oxymercuration. The effect of styrene structure on product distribution suggests that the decomposition of an oxythallated adduct proceeds via a carbonium ion intermediate resulting from loss of thallium(I). © 1969, American Chemical Society. All rights reserved.