The decomposition of organic hydroperoxides: Part III. Kinetics of the acid‐catalyzed decomposition of benzyl‐type hydroperoxides

The HClO4‐catalyzed decomposition of a number of alkylbenzyl hydroperoxides has been investigated by a study of the reaction kinetics in 50% w ethanol at 50°C. A Hammett relation (p = ‐4.57) has been found to exist for the decomposition of ring‐substituted α,α‐dimethylbenzyl hydroperoxides to the corresponding phenols and acetone, σ+ values giving the best correlation. An electrolyte effect has been observed in the decomposition of the hydroperoxides studied, the magnitude of which runs parallel to the reactivity of the various hydroperoxides. A qualitative explanation of this phenomenon can be given in terms of differences in solvation for the different transition state complexes. Data for the enthalpy and entropy of activation are in accordance with this assumption. Our results provide further support for the recently proposed mechanism of the acid‐catalyzed hydroperoxide decomposition. The effect of nuclear substituents and the observation of the electrolyte effect permit of a detailed description of the transition state complex. In the acid‐catalyzed decomposition of some substituted alkylbenzyl hydroperoxides other reactions have been encountered, which are discussed briefly.