Cumene oxidation scheme

The CLD methods for HPLC using isoluminol (190) with microperoxidase catalysis, for determination of lipid hydroperoxides in clinical fluids, have been reviewed. Determination of phospholipids hydroperoxides by luminol (124) CL has been reviewed . A fast RP-HPLC method (retention times 1 to 2 min) for determination of hydroperoxides and other peroxide compounds includes UVD, which is not always effective, and CLD, attained on injection of luminol (124), the CL reagent (Scheme 3), hemin (75a), a catalyst, and NaOH to raise the pH of the solution. A FLD cell may act as CLD cell if the excitation source is turned off. The selectivity of CLD is of advantage over UVD in industrial analysis thus, for example, UVD of a sample from a phenol production line based on cumene oxidation (equation 13) shows peaks for cumyl hydroperoxide (27), unreacted cumene, cumyl alcohol and acetophenone, whereas CLD shows only the 27 peak. The... 

The Schiff base-oxovanadium(IV) complex formulated as 19 was found to catalyze the asymmetric oxidation of sulfides with cumene hydroperoxide (Scheme 6C.8) [70]. Various aryl methyl sulfides were used for this process (room temperature in dichloromethane and 0,1 mol equiv. of the catalyst). Chemical yields were excellent, but enantioselectivities were not higher than 40% for the resulting methyl phenyl sulfoxide, Complex 16a, where [Ti] was replaced by VO, was also examined in the oxidation of sulfides, but the reactions gave only racemic sulfoxides [68],... 

Cumene manufacture consumed about 10 percent (2.2 billion lb) of the propylene used for chemicals in the United States in 1998. It is prepared in near stoichiometric yield from propylene and benzene with acidic catalysts (scheme below). Many catalysts have been used commercially, but most cumene is made using a solid phosphoric acid catalyst. Recently, there has been a major industry shift to zeolite-based catalyst. The new process has better catalyst productivity and also eliminates the environmental waste from spent phosphoric acid catalyst. It significantly improves the product yield and lowers the production cost. Cumene is used almost exclusively as feed to the cumene oxidation process, which has phenol and acetone as its coproducts. 

Phenol is a material of major commercial importance. One of its earliest uses was as a disinfectant (carbolic acid). Earlier in the twentieth century, it became important as a feedstock for resins such as Bakelite , and in the latter part of the century it also became very important as a precursor for caprolactone and caprolactam and hence polyester and polyamide manufacture. The two major methods for phenol production nowadays are by the catalytic oxidation of benzoic acid and catalytic decomposition of cumene hydroperoxide (Scheme 4.55). 

Most phenol nowadays is obtained from isopropylbenzene (cumene), which is oxidized by air in the cumene process (Scheme 4.1). Acetone (propanone) is a valuable by-product of the process and this route is a major source of this important solvent. The formation of cumene hydroperoxide proceeds by a free radical chain reaction initiated by the ready generation of the tertiary benzylic cumyl radical, which is a further illustration of the ease of attack at the benzylic position, especially by radicals (see Chapter 3). 

Since the rate of cumene oxidation at 100° is rather high, on this system, on-visible, it is necessary to work with small concentrations of nickel catalyst, which can facilitate a high yield of the hydroperoxide [8, 39]. It is evident from analysis of scheme of catalyzed hydrocarbons oxidation, including participation of catalyst in chain initiation reaction under catalyst interaction with ROOH and also in chain propagation (Ct + RO ), that with decrease in [Ct the rate of reaction should be decreased, and [ROOH] should be increased [8, 15]. It has appeared that together with... 

The first three cases of axial base coordination (scheme 3) do not lead to significant changes in the structure of the initial complex, i.e. they do not directly set free coordination positions, but they are very important in cases which will be studied further. Particular attention should be paid to the last three cases depicted in scheme 3 where the chelate ligands are shifted by the plane of the complex and one or two "free" coordination positions are obtained. Therefore such "adducts" may show catalytic activity. In particular, the last case is closely similar to the example with o-phenanthro-line, which "promote" the catalytic activity of copper acetylacetona-te complex during cumene oxidation. Similar structures were proved by the X-ray analysis(7,8) and also by EPR investigations(9). 

The scheme of the peroxides activation and decomposition in the presence of quaternary onium salt is proposed. It is substantiated by kinetic methods as well as by molecular modeling methods. It has been shown that peroxides decomposition in the presence of tetraethylammonium bromide proceeded according to supramolecular mechanism. Cyclohexanone peroxides in the presence of Et4NBr effectively initiate the radical chain cumene oxidation. 

Catalytic Oxidation Reactions. Cumene oxidation is performed by charging a reactor with benzene, cumene, and a catalytic amount of FeDPP3(S03CF3)2 (Scheme 1), underpressure with a constant O2 feed at 60°C (eq 4). A similar reaction is also observed with cyclohexane when exposed to the iron catalyst (FeDPP3(S03Cp3)2) under conditions involving higher pressures and temperatures (eq 5). ... 

Synthetic phenol capacity in the United States was reported to be ca 1.6 x 10 t/yr in 1989 (206), almost completely based on the cumene process (see Cumene Phenol). Some synthetic phenol [108-95-2] is made from toluene by a process developed by The Dow Chemical Company (2,299—301). Toluene [108-88-3] is oxidized to benzoic acid in a conventional LPO process. Liquid-phase oxidative decarboxylation with a copper-containing catalyst gives phenol in high yield (2,299—304). The phenoHc hydroxyl group is located ortho to the position previously occupied by the carboxyl group of benzoic acid (2,299,301,305). This provides a means to produce meta-substituted phenols otherwise difficult to make (2,306). VPOs for the oxidative decarboxylation of benzoic acid have also been reported (2,307—309). Although the mechanism appears to be similar to the LPO scheme (309), the VPO reaction is reported not to work for toluic acids (310). 

The mechanism of H02 formation from peroxyl radicals of primary and secondary amines is clear (see the kinetic scheme). The problem of H02 formation in oxidized tertiary amines is not yet solved. The analysis of peroxides formed during amine oxidation using catalase, Ti(TV) and by water extraction gave controversial results [17], The formed hydroperoxide appeared to be labile and is hydrolyzed with H202 formation. The analysis of hydroperoxides formed in co-oxidation of cumene and 2-propaneamine, 7V-bis(ethyl methyl) showed the formation of two peroxides, namely H202 and (Me2CH)2NC(OOH)Me2 [16]. There is no doubt that the two peroxyl radicals are acting H02 and a-aminoalkylperoxyl. The difficulty is to find experimentally the real proportion between them in oxidized amine and to clarify the way of hydroperoxyl radical formation. 

In the first of these techniques the lanthanoid complex (33) (5-8 mol%) is used as the organometallic activator in cumene hydroperoxide or tert-butyl hydrogen peroxide-mediated oxidation of chalcone (epoxide yield 99 % 99 % ee) or the ketone (34) (Scheme 20)[1001. 

Phenol is the major source of Bakelite and phenol resins, which are utihzed in many commodities worldwide phenol is also used as reagent for syntheses of dyes, medicines and so on. The industrial demand for phenol has increased every year and its production now exceeds 7.2 megaton year 94% of the worldwide production of phenol is processed in the cumene process. The cumene process involves the reaction of benzene with propene on acid catalysts like MCM-22, followed by auto-oxidation of the obtained cumene to form explosive cumene hydroperoxide and, finally, decomposition of the cumene hydroperoxide to phenol and acetone in sulfuric acid (Scheme 10.3) [73],... 

Aliphatic side chains of aromatics, such as cumene [65] and ethylbenzene [66] are oxidized to the corresponding alcohols and ketones by oxygen on FePcY and CoPcY respectively (Scheme 4). Propylene is oxidized on CoPcX to small amounts of carbon dioxide and acetone and higher amounts of formaldehyde and acetaldehyde [79]. 

The co-oxidation of cumene (CH) and Tetralin (TH) can be represented by the following simplified reaction scheme ... 

Dialkylzinc reagents combine with BINOL to generate, in situ, a catalyst for homogeneous epoxidation of (/y)-o /3-enoncs to the corresponding f raws-epoxy ketones. TBHP and cumene hydroperoxide (CHP) are effective terminal oxidants for this process ees of up to 96% have been achieved. Mechanistic investigations point towards an electrophilic activation (Scheme 11) of the substrates by the chiral BINOL-zinc catalyst and a subsequent nucleophilic attack of the oxidant227... 

The first example of a free-radical chain reaction successfully conducted in sc C02, which demonstrated the potential of this solvent for preparative scale chemistry, was a report from the McHugh group (Suppes et al., 1989) dealing with the oxidation of cumene (eq. 4.4). The propagation steps for this reaction are depicted in Scheme 4.11. Pressure (and thus viscosity) had little effect on the initiation, propagation, or termination rate constants. No unusual kinetic behavior was observed near the critical point. 

Oxidation of organic molecules with O2 (flameless) is referred to as autoxidation. The synthesis of cumene hydroperoxide from cumene is initiated by catalytic amounts of 2.36 as the radical initiator, which generates the cumyl radical A. The cumyl radical A reacts with O2 to give the radical B in the first propagation step and regenerated in the second propagation step, in which cumene hydroperoxide (2.62) is also formed (Scheme 2.48). 

Dihydroxybenzene may be prepared from 2-hydroxybenzaldehyde by the Dakin reaction, which involves oxidation in alkaline solution by hydrogen peroxide (Scheme 4.15). The reaction involves a 1,2-shift to an electron-deficient oxygen and is similar to the cumene process used to synthesize phenol (Section 4.2). 

On an industrial scale, phenol is obtained by the oxidation of isopropylbenzene (cumene). Initially a hydroperoxide is formed, which then undergoes a fragmentation and rearrangement. The initial oxidation illustrates the susceptibility of benzylic positions to oxidative, particularly radical, attack (Scheme 4.14). 

Scheme 5.2 reports the atom economy for two direct routes (using N2O or H2O2 as the oxidant) and for the commercial route via cumene. This example shows some of the problems in using this indicator to evaluate the greener" process. Are the direct routes better than the cumene route The problem is related to whether to consider... 

The direct oxidation of benzene into phenol constitutes one of the challenges in chemistry to substitute the cumene process at the industrial level. Such oxidation has also been achieved with several TpfCu complexes as catalysts, leading to moderate yields and high selectivity toward phenol, in a transformation using hydrogen peroxide as the oxidant and at moderate temperatures. The same catalytic system has been employed for the selective oxidation of anthracenes into anthraquinones (Scheme 24). 

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