Phosphate esters Phosphonates

Neutral Extractants. Many neutral organophosphoms extractants are available phosphate esters, phosphonate esters, phosphinate esters, and phosphine oxides. The most popular neutral extractant is tributylphosphate (TBP), which reacts with RE elements according to a solvation mechanism ... 

Table 45 Preparations Cobalt Phosphate, Phosphate Ester, Phosphonate and Phosphite Complexes...

FIGURE 12.20 Some applications of industrial phosphate esters. Phosphonate esters and phosphorothioate (thiophosphate) esters are also important in some of these applications. 

Most organophosphorus insecticides are based on a single P atom, which is linked directly to some combination of O, S, C or N atoms. These inclnde phosphate esters, phosphonates, amides and their thioated analogues. Comparatively few commercial insecticide molecules contain more than one P atom and these are usually pyrophosphate esters or their derivatives. Common types of insecticide inclnde those in Table 12.31. 

If alkyl groups are attached to the ylide carbon atom, cis-olefins are formed at low temperatures with stereoselectivity up to 98Vo. Sodium bis(trimethylsilyl)amide is a recommended base for this purpose. Electron withdrawing groups at the ylide carbon atom give rise to trans-stereoselectivity. If the carbon atom is connected with a polyene, mixtures of cis- and rrans-alkenes are formed. The trans-olefin is also stereoseiectively produced when phosphonate diester a-carbanions are used, because the elimination of a phosphate ester anion is slow (W.S. Wadsworth, 1977). 

The alkyl and alkoxy substituents of phosphate or phosphonate esters also affect the phosphorylating abiUty of the compound through steric and inductive effects. A satisfactory correlation has been developed between the quantitative measure of these effects, Tafts s O, and anticholinesterase activity as well as toxicity (33). Thus long-chain and highly branched alkyl and alkoxy groups attached to phosphoms promote high stabiUty and low biological activity. 

Much effort has been placed in the synthesis of compounds possessing a chiral center at the phosphoms atom, particularly three- and four-coordinate compounds such as tertiary phosphines, phosphine oxides, phosphonates, phosphinates, and phosphate esters (11). Some enantiomers are known to exhibit a variety of biological activities and are therefore of interest Oas agricultural chemicals, pharmaceuticals (qv), etc. Homochiral bisphosphines are commonly used in catalytic asymmetric syntheses providing good enantioselectivities (see also Nucleic acids). Excellent reviews of low coordinate (coordination numbers 1 and 2) phosphoms compounds are available (12). 

Monocyclohexyl phosphates and phosphonates can be cleaved by a two-step process in which the ester is treated with an epoxide such as propylene oxide to form another ester, which, upon treatment with base, releases the cyclohexyl alcohol. ... 

Phosphonates are organic phosphates characterized by a C-P-O bond, which is much more resistant to hydrolysis than the polyphosphate bond (O-P-O) or the phosphate ester bond (C-O-P), making them suitable for many types of BW treatment formulation. Phosphonates were originally developed for the industrial and institutional (I I) cleaning market in the 1960s, but are commonly employed in a myriad of applications. 

Phosphates and phosphonates are valuable contents of cleaners used for technical purposes especially when anticorrosive behavior is also required. Phosphoric acid esters are a component of aqueous cleaning compositions for printed circuit boards [212]. 

Emulsions are frequently used in the formulation of herbicides. Such emulsions have to form stable concentrates. They will be diluted with water before applying on plants. In this form too the surfactants used have to support the formation of fine droplets at the nozzles and provide a sufficient wetting of leaves. Surfactants have to be used which will not interfere with water hardness. Therefore phosphate esters and phosphonic esters are often applied. 

Furthermore, the GPO procedure can also be used for a preparative synthesis of the corresponding phosphorothioate (37), phosphoramidate (38), and methylene phosphonate (39) analogs of (25) (Figure 10.20) from suitable diol precursors [106] to be used as aldolase substrates [102]. In fact, such isosteric replacements of the phosphate ester oxygen were found to be tolerable by a number of class I and class II aldolases, and only some specific enzymes failed to accept the less polar phosphonate (39) [107]. Thus, sugar phosphonates (e.g. (71)/(72)) that mimic metabolic intermediates but are hydrolytically stable to phosphatase degradation can be rapidly synthesized (Figure 10.28). 

Phosphonate analogs to phosphate esters, in which the P—0 bond is formally replaced by a P—C bond, have attracted attention due to their stability toward the hydrolytic action of phosphatases, which renders them potential inhibitors or regulators of metabolic processes. Two alternative pathways, in fact, may achieve introduction of the phosphonate moiety by enzyme catalysis. The first employs the bioisosteric methylene phosphonate analog (39), which yields products related to sugar 1-phosphates such as (71)/(72) (Figure 10.28) [102,107]. This strategy is rather effective because of the inherent stability of (39) as a replacement for (25), but depends on the individual tolerance of the aldolase for structural modification close... 

Biodegradable polyurethanes have been proposed and studied before (9-72). The difference in our study is the inclusion of a phosphoester linkage instead of the commonly used polyester component. This seems to provide more flexibility as the side chain of the phosphate or phosphonate can be varied. For controlled drug delivery applications, drugs can be linked to this site to form a pendant delivery system. Moreover, for certain medical applications, fast degradation rate is obtainable by the introduction of these hydrolyzable phosphoester bonds. With the LDI based polyurethanes, drugs or other compounds of interest can also be coupled to the ester side chain of the lysine portion. 

Cambella and Antia [385] determined phosphonates in seawater by fractionation of the total phosphorus. The seawater sample was divided into two aliquots. The first was analysed for total phosphorus by the nitrate oxidation method capable of breaking down phosphonates, phosphate esters, nucleotides, and polyphosphates. The second aliquot was added to a suspension of bacterial (Escherichia coli) alkaline phosphatase enzyme, incubated for 2h at 37 °C and subjected to hot acid hydrolysis for 1 h. The resultant hot acid-enzyme sample was assayed for molybdate reactive phosphate which was estimated as the sum of enzyme hydrolysable phosphate and acid hydrolysable... 

Redmore, D., Chemistry of phosphorous acid new routes to phosphonic acids and phosphate esters, ]. Org. Chem., 43, 992, 1978. 

A phosphate-phosphonate rearrangement process has also been explored in which a strong base is used to abstract a proton from the position adjacent to an aryl phosphate ester linkage. The product, an or f/io-phosphonopheno I, is generated in excellent yield (Figure 6.16).70 Further exploration of the variability of structure for this type of reaction seems desirable. 

Collectors from the PM series were specifically developed for beneficiation of niobium ores that contain nepheline/cyanite as the major gangue minerals. The collector is composed of a mixture of phosphate ester collector (SM15, Clariant) and phosphonic acid treated with octanol. From an ore that assays 0.5% Nb20s, a concentrate grade of 49% Nb205 at a recovery of 73% was achieved. 

Aryloxytitanium halides, 25 83 2-Arylpyridines, 27 111 Aryl phosphate esters, 79 51 Aryl phosphates, 7 7 493 Aryl phosphonates, 79 37 Arylphosphorus compounds, 79 28 Aryls, palladium, 79 652 Aryl-silicon compounds, 22 553, 554 Arylsulfinic acids, 27 248-249 Arylsulfonylated gelatin, 72 444 Aryltin trihalides, 24 810-811 Arylyl amines, 70 396-399 Asahi Chemical Industries EHD processes, 9 676-677 sebacic acid production, 9 679-680 ASAM (alkaline-sulfite-AQ-methanol) process, 27 30... 

In this chapter, the words cleavage and de-esterification are often used to make it clear that reactions other than hydrolysis may be involved in the breakdown of some inorganic esters. This is particularly true for nitrates, and various phosphates and phosphonates, as discussed in the relevant sections. 

Dobry, A. and Keller, R. Vapor pressures of some phosphate and phosphonate esters, / Phys. Chem., 61(10) 1448-1449,1957. 

---