Phase transfer oxidation

Phase-transfer oxidation is a technology for destruction of organic contaminants. It was developed to treat contaminated liquid streams using adsorption for contaminant removal and advanced oxidation processes for spent adsorbent regeneration. It was used in testing to treat the contaminated effluent from groundwater extraction technologies. 

The use of a quaternary ammonium hydroxide as a phase transfer catalyst provides an efficient conversion of xanthene (174) to xanthone under mild conditions (77TL2117), while the use of permanganate under milder conditions than those shown in Scheme 9 enables flavenes such as (175) and (176) to be converted into flavones (77BCJ3298, 78BCJ1175). The phase transfer oxidation requires strongly alkaline conditions which may render it less suitable for the oxidation of flavenes and chromenes. Xanthene has also been converted into xanthone by means of permanganate or chromic acid. 

Phase transfer oxidation of alkenes Ru04/NaI04, 0s04... 

Phase transfer oxidative cleavage of cycloalkenes Ru04/NaI04 in h2o/co2 Morgenstern et al. (1996)... 

Perhydrophenalene, 61, 103 PERHYDRO-9b-PHEN ALENOL, 61, 103 2-(PERHYDRO-9 b-PHEN ALYL)-1,3,2-DIOXABOROLE, 61, 103 Phase transfer alkylation, 60, 67 Phase transfer oxidation, 60, 13 1 //-Phenalene, 61, 103 Phenalene, 9ba-chloro-... 

The variation of wastewater quality is related to the human activities (and thus time dependent as shown before) but also to some physico-chemical factors occurring along the sewer. Fresh organic matter composition can vary from the source (houses, for example) to the treatment plant because of physico-chemical phenomena (solids settling, phase transfer, oxidation, etc.). 

Oxidations. Allylic and benzylic alcohols are converted to the aldehydes with great selectivity by a Cr-mediated oxidation with sodium percarbonate. The phase-transfer oxidation of anilines with KMn04 results in azoarenes. ... 

Sulfoxides. In the phase-transfer oxidation of sulfides, saturated NaHCOj is added. The stoichiometry of NaOCl controls the oxidation at one or both sulfur atoms of bis(phenyltfiio)alkanes. 

Selective oxidation of benzyl chloride to benzaldehyde is another reaction of great commercial importance. There exist several methods to prepare benzaldehyde, both commercially and synthetically, but the oxidation of benzyl chloride directly to benzaldehyde in a single pot by using CM-PTC merits special attention. We have studied in our laboratory [3] the kinedcsand mechanism of the liquid-liquid and solid-liquid phase transfer oxidation by using chromate and hypochlorite s ts and it was thought desirable to study the selectivity engineering aspects of this reaction. 

The base-catalyzed autoxidation of p-nitrotoluene (PNT) yields the corresponding benzoic acid and dimeric products [27]. Remarkably, ultrasonic agitation steers the phase transfer oxidation of PNT, o-nitrotoluene, o-ethylnitrobenzene and p-ethylnitrobenzene toward the carboxylic acid [28]. 

Supercritical carbon dioxide represents an inexpensive, environmentally benign alternative to conventional solvents for chemical synthesis. In this chapter, we delineate the range of reactions for which supercritical CO2 represents a potentially viable replacement solvent based on solubility considerations and describe the reactors and associated equipment used to explore catalytic and other synthetic reactions in this medium. Three examples of homogeneous catalytic reactions in supercritical CC are presented the copolymerization of CO2 with epoxides, ruthenium>mediated phase transfer oxidation of olefins in a supercritical COa/aqueous system, and the catalyic asymmetric hydrogenation of enamides. The first two classes of reactions proceed in supercritical CO2, but no improvement in reactivity over conventional solvents was observed. Hythogenation reactions, however, exhibit enantioselectivities superior to conventional solvents for several substrates. 

Hantzsch 1,4-dihydropyridmes to pyridines using cetyltrimeth-ylammonium peroxodisulfate a phase transferring oxidant. 

These will be the subject of the sections to come. Because of the limitations of space, subjects such as enzymatic oxidation, the use of polyoxometalates in oxidation reactions, oxidations mediated by metal nanoparticles, oxidation of bioavailable feedstocks, oxidation of water to dioxygen, organocatalytic asymmetric oxidations and asymmetric phase transfer oxidations are not covered in this chapter. 

---