Alkylaromatic kinetic acidity

The intramolecular selectivity in the deprotonation of alkylaromatic radical cations has been investigated in a series of 5-X-l,2,3-trimethylbenzene radical cations the results showed that spin and/or charge density at the scissible C H bond can strongly influence the kinetic acidity, which is, accordingly, very sensitive to the nature and position meta or para) of ring substituents (Scheme 32) [149]. 

Emulsion oxidation of alkylaromatic compounds appeared to be more efficient for the production of hydroperoxides. The first paper devoted to emulsion oxidation of cumene appeared in 1950 [1], The kinetics of emulsion oxidation of cumene was intensely studied by Kucher et al. [2-16], Autoxidation of cumene in the bulk and emulsion occurs with an induction period and autoacceleration. The simple addition of water inhibits the reaction [6], However, the addition of an aqueous solution of Na2C03 or NaOH in combination with vigorous agitation of this system accelerates the oxidation process [1-17]. The addition of an aqueous phase accelerates the oxidation and withdrawal of water retards it [6]. The addition of surfactants such as salts of fatty acids accelerates the oxidation of cumene in emulsion [3], The higher the surfactant concentration the faster the cumene autoxidation in emulsion [17]. The rates of cumene emulsion oxidation after an induction period are given below (T = 353 K, [RH] [H20] = 2 3 (v/v), p02 = 98 kPa [17]). 

Kinetics of oxidation of toluene and cumene to the corresponding a-hydroxy compounds by stoich. trani-[Ru(0)(bpy)(tpy)] VCH3CN were reported a two-electron hydride-ion transfer step may be involved [672]. Electro-oxidation of side-chains in alkylaromatics by [Ru(0)(bpy)(tpy)] (generated electrochemicaUy in situ from [Ru(OH)(bpy)(tpy)] V BuOH/water pH 6.8/Pt electrodes/50°C) was effected toluene gave benzoic acid and ethylbenzene gave acetophenone (Table 4.1) [673]. 

Metal bromide catalysis is widely used in industry for oxidation of alkylaromatic compounds to their corresponding acids. The mechanism for this catalytic process has been investigated for over 20 years but it is still not established despite numerous papers on this subject This work presents results of our investigations on the kinetics and mechanisms of cobalt bromide catalysis. 

The reaction of alkyl- and halo-substituted phenols with Cr02Cl2 results mainly in the formation of quinones and diphenoquinones. Phenoxyl radicals are involved as intermediates. The mechanism of oxidation of a-hydroxycar-boxylic acids by pyridinium chlorochromate involves a rate-limiting hydride transfer. In the reaction of HOCD2CO2H, a kinetic isotope effect (W d) = 5.80 has been determined. Spectroscopic evidence for Cr(IV) and Cr(V) species has been obtained in the oxidation of alkylaromatics by chromyl acetate in acetic anhydride.Stopped-flow and esr studies show two stages (equations 22, 23) in the reactions of RCH2Ph, with both rates being decreased on deuteration at... 

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