Oxidative phosphotungstic compounds

Desulfurization using purified enzymes Investigations into enzymatic desulfurization as an alternative to microbial desulfurization has revealed several enzymes capable of the initial oxidation of sulfur. A study reported use of laccase with azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) as a mediator for oxidation of DBT [181]. The rate of this reaction was compared to hydrogen peroxide-based phosphotungstic acid-catalyzed oxidation and the latter was found to be about two orders of magnitude higher. The authors also oxidized diesel oil sulfur to no detectable levels via extraction of the oxidized sulfur compounds from diesel. In Table 9, the enzymes used in oxidation of DBT to DBTO are reported. 

Phosphotungstic acid crystallizes from water (in which it is extremely soluble) in very heavy white octahedra. The water solution is not stable toward light but slowly turns blue as a result of reduction. Re-oxidation is easily effected by heating with chlorine water. In spite of its great solubility in water, the acid may be completely extracted from water solution by ether. It forms with ether a dense liquid layer of a complex compound which is insoluble both in ether and in water, so that three liquid layers are formed when the water solution is extracted with an excess of ether. In addition to being very soluble in water and ether, phosphotungstic acid is readily soluble in the lower alcohols and esters. 

Total wine polyphenols are oxidised by the Folin-Ciocalteu reagent - composed of a mixture of phosphotungstic and phosphomolybdic acids which are reduced by the oxidation of the phenols, forming a mixture of blue oxides of tungsten and molybdenum. The blue coloration has an absorption maximum at approximately 750 nm, the intensity of which is proportional to the level of phenolic compounds present in the wine. The sequential analyser method is a direct automation of the manual method and results are expressed as a unit-less index. 

Penicilin-G (4 g, 10.8 mmol), water (40 ml), and the catalyst ((NH4)eMo7024-A26) (0.5 g) were charged to a three necked flask, fitted with, thermometer, cooling bath, overhead stirrer, and peristaltic pump, was equilibrated to 20 °C. H2O2 (35 % w/w. 1.04 g, 10.8 mmol) was added via the pump over 45 mins. On completion of the H2O2 addition, the reaction was maintained under these conditions for a further 45 mins. Analysis of the reaction was via H.P.L.C. and comparison to the authentic compound. Benzenethiol was also oxidized using phosphotungstic acid on alumina. However, the solvent was t-butanol, and the reaction temperature was 80 °C for 4 h. 

Table 38.2 gives the conductivity of crystalline materials, all containing some water molecules, and used in ECDs. Phosphotungstic acid (PWA) has been used either as an electrochromic electrolyte able to undergo a colour change during oxidation or as an electrolyte or associated with WOj . Zirconium phosphate showed a good conductivity but a fast dissolution of WO3 was observed similar to that found with WO3 in pure water . However, both compounds are susceptible to variations of the hydrated water content and react with WO3 films. Compared to the above... 

Recently, however, formation of a red Cm(iv) complex in phosphotungstate solution was achieved by the use of peroxydisulfate as the oxidant [53], Kosyakov et al. [54] demonstrated that in such solutions the Cm(iv) is reduced much faster than can be accounted for by radiolytic effects, while Am(iv) in such solutions is much more stable, being reduced at a rate attributable to radiolytic effects alone. No value for the E° (Cm /Cm ) is known but from existing data it is substantially more positive than E° (Am /Am ) and probably about as positive as °(Pr /Pr ). The recent success of generating soluble carbonate solutions of Pr(iv) suggests that similar soluble Cm(iv) species may be prepared [55], All known Cm(iv) compounds are either fluorides or oxides, but a broader chemistry has been developed for Cm(iii). 

These compounds are characterized by a very unpleasant odor if they have a sufficiently high vapor pressure. Among color reactions used for their detection, those with sodium nitroprusside, phosphotungstic acid, and nitrous acid are most commonly used. The preparation of heavy-metal salts is important both for detection and identification also used for identification are the reactions with 2,4-dinitrochlorobenzene, m-nitrobenz-amide, or (for chromatography) 3,5-dinitrobenzoyl chloride and 2,4-di-nitrophenylsulfenyl chloride (see (1)]. On mild oxidation mercaptans give disulfides —for example, with iodine,... 

Wang S-S, ZhangJ, Zhou C-L, Vo-Thanh G, Liu Y. An ionic compound containing Ru(III)-complex cation and phosphotungstate anion as the efficient and recyclable catalyst for clean aerobic oxidation of alcohob. Catal Commun. 2012 28 152-154. 

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