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The reaction of nitrosobenzene with zerz-butyl hydroperoxide in benzene or cyclohexane, as initiated by di-terz-butyl peroxyoxalate or by hydrocarbon-soluble /3-diketonates of a number of transition metals, yields nitrobenzene rapidly and quantitatively. The rate law observed for the peroxalate-initiated reaction is consistent with a radical chain mechanism involving both z-BuO• and z-Bu02•, in which z-BuO • is diverted, in part, to the spin adduct Ph(BuO)NO •, conversion to nitrobenzene occurs by oxygen-atom transfer from Z-Bu02 •, and the principal mode of termination is the reaction of z-Bu02• with Ph(BuO)NO•. Changes in the kinetic picture when metal chelates are substituted for peroxalate reflect variation in the modes of initiation. Catalytic action by the dipivaloylmethane chelate of Co(II), Co(dpm)2 (which is rapidly converted to a mixture of Co11 and Co111 under the reaction conditions), and by Mn(acac)3, appears to occur via a straightforward two-step initiation sequence in which the 2+ state of the metal reacts with hydroperoxide, yielding BuO•, after which the 3+ state reacts with a second hydroperoxide, yielding Bu02 •. Overall specific rates for initiation in these cases are determined principally by the rate constant for the second step. The fully chelated and substitution-inert Co(dpm)3 exhibits practically no catalytic activity under our conditions. Catalysis by VO(dpm)2 is complicated by the formation of a complex, VO(dpm)2-Bu02H (Kassn = 1.9 X 10a M_1 at 25°), which may undergo unimolecular homolysis, forming BuO•, or, alternatively, may react with a second hydroperoxide, again forming BuO•. Cyclization of vanadium between the 4 + and 5+ oxidation states occurs. Catalysis by Pb(dpm)2 involves two lead centers in the initiation sequence and is subject to competitive inhibition by high concentrations of hydroperoxide. A bimolecular reaction between two units of Pb(dpm)2-Bu02H, yielding two butoxide radicals and PbIV, is proposed as the rate-determining step in a path which retains the free-radical character of the catalyzed oxidation but bypasses Pbm.

was decolorized with activated charcoal and recrystallized several times from ether-pentane, yielding 10.5 g (51%) of fine orange needles: mp 92-93°; nmr (CCU) 5 Ar H's,8), 4.46, 4.16

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