In phenol oxidation

Figure 10. Photocatalytic activity of Au/titania nanocomposites containing 0 to 5 % Au in phenol-oxidation and chromium-reduction reactions [57].

Figure 10. Reactor designs in phenol oxidation reaction [30].

In phenolic oxidative coupling reactions, these phenol-derived radicals do not propagate a radical chain reaction instead, they are quenched by coupling with other radicals. Thus, coupling of two of these resonance structures in various combinations gives a range of dimeric systems, as shown. The... 

Yields of dimer in phenol oxidations are often decreased by competing reactions such as subsequent oxidation of the dehydro dimer or the anodically hydro-... 

Nucleophilic solvents change the products, since they participate in phenolic oxidation, as amply demonstrated with methanol. A great number of phenols... 

Studies directed toward the synthesis of amaryllidaceae alkaloids provide instructive examples of the combined use of spirocylization and Michael addition pathways in phenolic oxidations (03MI1). For example, treatment of the norbelladine derivative 164 with BTIB leads, by way of C,C-bond formation, to the spiroannulated azepine 165 (Scheme 47) (96JOC5857, 98JOC6625). Hydrolysis of the amide moiety in 165 results in Michael addition of the nitrogen center to the dienone ring and affords ( )-oxomaritidine (166). BTIB-oxidation of the appropriate... 

Shukla SP, Devi S (2005) Covalent coupling of peroxidase to a copolymer of acrylamide (AAm)-2-hydroxyethyl methaacrylate (HEMA) and its use in phenol oxidation. Process Biochem 40 147-154... 

The first reduced intermediate, Compound II, is formed when the n cation radical is reduced and a proton is transferred to the distal base (His). Compound II is then reduced to the Feln resting state with the simultaneous formation of water [70]. This second electron transfer step is one to two orders of magnitude slower than Compound I formation and is usually rate-limiting [72]. For HRP, the rate constant for Compound I formation (kfj is 2.0 x 107 M 1s 1 [73], while the rate-limiting step in phenol oxidation by HRP has a rate constant k 3.0 x 105 M 1s 1 [74, 75]. 

Potassinm or sodinm permanganate nnder protic and aprotic conditions is well known to be effective for phenohc oxidation leading to qninones and C—C and/or C—O con-pled prodncts. Some typical examples demonstrate the ntUity of barium manganate and methyltributylammonium permanganate in phenolic oxidation. 

Tryba, B., M. Inagaki, M. Toyoda, and A.W. Morawski, FTIR studies of the surface of Ti02, Fe-TiOj and Fe-C-Ti02 photocatalysts in phenol oxidation via the photo-Fenton process. J. Adv. Oxid. Tech. 10 (2007) 25-30. 

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