Diphenylmethyl hydroperoxide

In the absence of DMSO the conversion of diphenylmethyl hydroperoxide to benzophenone apparently does follow Reaction 6, at least in alcohol-containing solvents. The stoichiometry becomes nearly one mole of oxygen per mole of diphenylmethane, and the carbinol is eliminated as an intermediate. Table I lists the observed stoichiometries and initial rates of oxidation of diphenylmethane. In pyridine-, DMF-, or HMPA-containing solvents, a high yield of benzophenone was isolated upon hydrolysis after oxygen absorption had ceased. In pure HMPA there was considerable evolution of oxygen upon hydrolysis. 

Howard and Ingold studied this equilibrium reaction in experiments on the oxidation of tetralin and 9,10—dihydroanthracene in the presence of specially added triphenylmethyl hydroperoxide[41]. They estimated the equilibrium constant K to be equal to 60 atm-1 (8 x 103 L mol-1, 303 K). This value is close to T=25atm-1 at 300 K (A/7=38kJ mol-1), which was found in the solid crystal lattice permeable to dioxygen [84], The reversible addition of dioxygen to the diphenylmethyl radical absorbed on MFI zeolite was evidenced and studied recently by the EPR technique [85],... 

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