Carboxylic acids with cumene hydroperoxide

The decomposition of carboxyl radical occurs very rapidly, and C02 is formed with a constant rate in the initiated co-oxidation of cumene and acid [104]. Cumylperoxyl radical attacks the a-CH2 group of the carboxylic acid with the formation of a labile hydroperoxide. The concentration of this hydroperoxide increases during oxidation till it reaches a stationary concentration [RCH(OOH)-COOH]st = pi2[RCH2COOH][CuOO ]/A d. This reaction produces C02 with acceleration during some period of time equal to the time of increasing the a-carboxyhydroperoxide concentration. 

The effectiveness of lead tetra-alkyls can be degraded by the presence of sulphur compounds and enhanced by certain organic co-anti-knocks. Graiff [44] has shown that the latter effect is due to the formation of different forms of lead monoxide (red and yellow), with different catalytic activities [39]. The co-anti-knocks may be carboxylic acids or esters like r-butyl acetate [45] but, surprisingly, r-butyl and cumene hydroperoxides also work as co-anti-knocks with lead [44]. That is, when added to leaded... 

The unusual oxidant nickel peroxide converts aromatic aldehydes into carboxylic acids at 30-60 °C after 1.5-3 h in 58-100% yields [934. The oxidation of aldehydes to acids by pure ruthenium tetroxide results in very low yields [940. On the contrary, potassium ruthenate, prepared in situ from ruthenium trichloride and potassium persulfate in water and used in catalytic amounts, leads to a 99% yield of m-nitrobenzoic acid at room temperature after 2 h. Another oxidant, iodosobenzene in the presence of tris(triphenylphosphine)ruthenium dichloride, converts benzaldehyde into benzoic acid in 96% yield at room temperature [785]. The same reaction with a 91% yield is accomplished by treatment of benzaldehyde with osmium tetroxide as a catalyst and cumene hydroperoxide as a reoxidant [1163]. 

Oxidative esterification of arenes with carboxylic acids produces aryl esters, which can be used as precursors to valuable phenol derivatives (Scheme 8.6). Commercial production of phenol involves the aerobic oxidation of cumene to cumene hydroperoxide, followed by conversion to acetone and phenol under acidic conditions (Hock process) [49]. Aerobic acetoxylation of benzene to phenyl acetate provides a potential alternative route to phenol, and Pd-catalyzed methods for this transformation have been the focus of considerable effort. None ofthese methods are yet commercially viable, however. 

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