Substituent Effects in the Decomposition of t-Alkyl t-Butyl Peroxides

Article abstract of DOI:10.1246/bcsj.64.259

The decomposition rates and products of various t-alkyl t-butyl peroxides were examined in cumene at several temperatures.The decomposition of these peroxides took place homolytically, depending on the structure of the t-alkoxyl moieties (RC(CH3)2-O), and was retarded in the order: R = (CH3)3CCH2 > (CH3)2CH > CH3CH2CH2 > PhCH2 > CH3CH2 > ClCH2 > CH3.The rate constants for the electron-donating alkyl substituents at 150 deg C are correlated very well to a Taft equation (log k_d = -10.93Σ?*-6.61 (correlation coefficient of 0.9501)), which is fairly different from the equation log k_d = -0.131Σ?*-3.422 for electron-withdrawing polar substituents.From this correlation and a product analysis, the nature of the polar character at the transition state of the decomposition is discussed.