Ceric ammonium sulfate quinones

Oxidation of arenes This oxidant is somewhat superior to CrOs for oxidation of arenes to quinones but less efficient than ceric ammonium sulfate (8,80-81). An example is the oxidation of naphthalene to 1,4-naphthoquinone in 75% yield. 

Ammonium cerium sulfate (ceric ammonium sulfate), (NH4)2Ce-(804)4 2(NH4)2S04 2H20, converts aromatic polynuclear hydrocarbons into quinones [429]. 

Quinones (Table 6.10, item 4) are formed only with difficulty from benzene (CfiH ) itself. However, as shown in Equations 6.77 and 6.78, on oxidation in solution with, for example, ammonium cerium(IV) sulfate [ceric ammonium sulfate, Ce(NHi)4(S04)4], naphthalene (CioHg) and anthracene (C14H10) yield p-quinones and phenanthrene (C14H10), an isomer of the latter (Equation 6.79), yields an o-quinone much more readily. It has been argued that maintaining aromaticity in portions of each of these polynuclear systems aids in making the oxidation reaction much more facile. Similar oxidation patterns are common in naturally occurring quinones. 

Phenols (e.g., phenol itself [CeHs-OH or Ar-OH], Table 6.10, item 2) and their esters (e.g., the trifluoroacetate ester of phenol [C6H5-O2CCF3 or Ar02CCH3], Table 6.10, item 3) have been oxidized with air and oxygen (O2), in neutral and alkaUne solutions, with and without ionic and/or radical catalysts and/or irradiation and in a variety of solvents. Enzymes (this chapter and Chapter 12) from a wide variety of sources have also been used. Frequently, oxidation of aromatic systems to phenols cannot be stopped before quinones and products of ring fragmentation occur and numerous, sometimes ill-defined, products result. Thus, as shown in Equation 6.80, oxidation of the polynuclear hydrocarbon chrysene with anunonium cerium(IV) sulfate [ceric ammonium sulfate, Ce(NH,)4(S04)4] is reported to produce 6H-benzo[d]naphtho[l,2-/>]pyran-6-one (8% yield) and a quinone (23% yield). The remainder of the product(s) (69%) was unidentified. 

This may relate to the oxidizing effect of sulfuric acid on the poly-hydric alcohol structure of lignin and its transformation into the quinonoid form. Oxidation of the polyhydric alcohol of lignin into quinone has been achieved on using ceric ammonium sulfate which inhibited graft polymerization reactions on using this initiator. ... 

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