Phosphites oxidation

When a phosphite is used as a catalyst modifier, it is susceptible to oxidation in the same manner as a phosphine. Unlike triphenylphosphine oxide, which is relatively innocuous except for precipitation when the solubility limit is reached, phosphite oxidation products may hydrolyze to give phosphoric acid. Since phosphites are esters, phosphoric acid can catalyst additional hydrolysis. Other than limiting formation of phosphite oxidation products, the best approach is to include some acidity control technology in the separation or reaction system. 

The situation is different for aryl phosphites, which give rise to shorter chains than alkyl phosphites do (about 100 elementary reactions). The rate of aryl phosphite oxidation, v v suggests that chains are terminated in a linear manner [4,14,27]. Linear chain termination was interpreted in terms of the following mechanism of chain oxidation of aryl phosphites ... 

Schink B, Friedrich M. 2000. Phosphite oxidation by sulphate reduction. Nature 406 37. 

Ethylene - vinyl acetate - acrylic acid teii)olymers have been crosslinked with 2,4 6-tri(2-methyl-l-aziridinyl)s-triazine or tris(2-methyl-l-aziridinyl) phosphite oxide. The in rovement in film tensile strength and the reduced solubility in triohlor ethylene are very marked. (49)... 

Schink B. and Friedrich M. (2000) Phosphite oxidation by sulfate reduction. Nature, 406. 

This group was developed for 5 -hydroxyl protection in oligonucleotide synthesis. It is stable to the conditions for nucleotide coupling using the phosphoramidite approach. It is not stable to acid or to 12/pyridine/THF, conditions used for phosphite oxidation. It has been used to prepare a 20-mer. ... 

Figure 2 (a) The native monoester phosphatase activity, and the promiscuous phosphite oxidation reactions catalyzed by alkaline phosphatase. Adapted from K. Yang W. W. Metcalf, Proc. Natl. Acad. Sci. U.S.A. 2004,101,7919-7924. (b) The active site arrangement of alkaline phosphatase with a bound transition state model. Adapted from I. Catrina P. J. O Brien J. Purcell I. NIkollc-Hughes J. G. Zalatan A. C. Hengge D. Herschlag, J. Am. Chem. Soc. 2007, 129, 5760-5765. 

Enrichment cultures have been tried repeatedly in the past to search for bacteria that can utilize reduced phosphorus compounds as electron donors in their dis-similatory metabolism. Both hypophosphite and phosphite could be excellent electron donors for a microbial energy metabolism because their oxidation releases electrons at very low redox potentials (Table 1). So far, only one bacterium has been isolated that can run its energy metabolism on the basis of phosphite oxidation to phosphate. 

Failure to demonstrate the activity of the phosphite-oxidizing enzyme in vitro so far may be due to the fact that we did not find the right cosubstrate for this enzyme yet. Our sulfate-reducing bacterium cannot oxidize hypophosphite or any other reduced phosphorus compounds. Interestingly, there are no... 

The high phosphate concentration in cells might indicate the abundance of phosphorus compounds in the primordial waters [85,251,252]. Since the concentration of phosphate in sea water is low (the phosphates of Ca and Mg are poorly soluble in water), it has been argued that more reduced compounds such as hypophosphite (phosphinate, P022-) and/or phosphite (phosphonate, P033-), which have better solubility in sea water, could have been abundant in the primeval, more reduced ocean [252-258]. This suggestion is supported by findings of diverse systems of hypophosphite and phosphite oxidation in prokaryotes (see [259] for a review). 

Phosphites are used alone or as co-stabilizers in combination with sterically hindered phenols. They act as oxygen scavengers, preventing discoloration during processing. Moreover, they reduce the generated hydroperoxides to alcohols and thus disrupt the radical chain reaction. The phosphites oxidize to phosphates in this reaction. Fig. 3.18. 

Ozone trimethyl phosphite Oxidative cleavage and ring opening Oxo compounds from ethylene derivatives... 

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