Green oxidants

Praseodymium is soft, silvery, malleable, and ductile. It is somewhat more resistant to corrosion in air than europium, lanthanum, cerium, or neodymium, but it does develop a green oxide coating that spalls off when exposed to air. As with other rare-earth metals, it should be kept under a light mineral oil or sealed in plastic. 

Due to its broad scope, as well as to its favorable features (commercial availability of the catalyst, use of a "green" oxidant, economy, extremely simple procedure and work-up), this method has been rapidly accepted, as demonstrated by its use by several different research groups, despite its recent disclosure.1617 This procedure employing CH3Re03 and UHP appears to be the method of choice when optically active nitrones are prepared by oxidation of the corresponding amines.14 15 18... 

Noyori, R., Aoki, M., Sato, K. (2003) Green Oxidation with Aqueous Hydrogen Peroxide. Chemical Communications, 1977-1986. 

VI. The Activity-Stability Parameterization of Homogeneous Green Oxidation Catalysts... 

Green Oxidation of Alcohols using Biominetic Cu Complexes and Cu Enzymes as Catalysts Isabel W.C.E Arends, Patrick Gamez and Roger A. Sheldon... 

Green Oxidation of Alcohols using Biominetic Cu Complexes and Cu Enzymes as Catalysts... 

Praseodymium is a silvery-white, soft metal that is easily formed into various shapes. When the pure metal is exposed to the air, a green oxide coating forms on its surface. To prevent oxidation, praseodymium is usually kept in oil in a covered container. 

The MIL-supported POM eatalysts were eharaeterized by elemental analysis, XRD, N2 adsorption, and FT-IR-speetroseopy, whieh indieated the preservation of both MIL and POM structures after immobilization. The eomposite M-POM/MIL-101 materials demonstrated fairly good catalytie performanee in a-pinene allylie oxidation (81-84 % verbenol/verbenone seleetivity at 15-25 % substrate eonversion) and earyophyllene epoxidation (100 % selectivity at 88 % conversion) with green oxidants - H2O2 (Ti-POM) and O2 (Co-POM) [126]. 

Green cubic crystals transforms to a grayish black octahedral form, known as black oxide, when strongly ignited black oxide has a metallic luster density of green oxide is 6.72 g/cm Mohs hardness 5.5 melts at 1955°C insoluble in water soluble in acids at ordinary temperatures black form dissolves in hot acids. 

Pale yellow metal attains a green oxide coating on exposure to air exhibits two crystalline modifications (1) an alpha form, that has a hexagonal close-packed structure, a density of 6.773 g/cm and a molar volume 20.82 cc/mol, and (2) a beta form that has an open body-centered cubic structure having a density of 6.64 g/cm and a molar volume of 21.20 cc/mol. The alpha form transforms to beta at 792°C. 

In 1823 J. A. Arfwedson reduced the green oxide of uranium (then believed to be the lowest oxide) with hydrogen, and obtained a brown powder which he took to be the metal, but which is now known to be uranous oxide, U02 (25, 30). In 1841 Peligot, on analyzing anhydrous uranous chloride, UC14, found that 100 parts of this chloride apparently yielded about 110 parts of its elements uranium and chlorine. His explanation of this seemingly impossible result was that the uranous chloride reacts with water in the following manner ... 

Organic Reactions in Micro-Organized Media—Why and How Water-Promoted Organic Reactions The design of green oxidants Water as a solvent for chemical reactions Water as a benign solvent for chemical syntheses... 

The epoxidation of olefins catalyzed by iminium salts and amines (or ammonium salts) is emerging as a new technique for the functionalization of simple aUcenes. These catalysts have relatively simple structures and hence are easily produced at scale they offer potential as green oxidation catalysts. These organic salts are effective oxygen transfer reagents towards electron-rich unfunctionalized olefins. For the iminium salt systems oxone oxidizes an iminium salt to the oxaziridi-nium intermediate, which then transfers oxygen to the olefin and as oxone reacts readily with iminium ions to regenerate the oxaziridinium species catalyti-cally, efficient oxidation is possible. 

A new reagent, AMiydroxyphthalimide combined with Co(acac)n (n = 2,3), transforms alkylbenzenes to ketones, whereas methylbenzenes give the corresponding carboxylic acids.1121 Phthalimide N-oxyl was found to be the key intermediate. Novel oxoperoxo Mo(VI) complexes mediate the cost-effective and environmentally benign oxidation of methylbenzenes to carboxylic acids.1384 Similar green oxidation of p-xylene to terephthalic acid was reported by using a Ru-substituted heteropolyanion.1385... 

To date, many soluble transition metal-based homogeneous catalysts including POMs have been developed for H202- and 02-based green oxidations. They are usually dissolved in reaction solutions, making all catalytic sites accessible to... 

Ketones, I COR2, have been converted to their -dihydroperoxides (112) using a green oxidant, aqueous 30% hydrogen peroxide, with iodine as catalyst.337 The iodine may enhance the electrophilic character of the carbonyl carbon and/or the nucleophilicity of the hydrogen peroxide. The reaction has also been extended to... 

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