Phosphorous acid trialkyl esters

P(0H)3 Phosphoric acid (phosphate esters trialkyl phosphate) Phosphorsaiire... 

Dialkyl sulfates aie esters of sulfuric acid, trialkyl phosphites ar e esters of phosphorous acid (H3PO3), and trialkyl phosphates are esters of phosphoric acid (H3PO4). 

The orthophosphoric acid is a three-basic acid that can form three kinds of esters by reaction with alcohols. If all three OH groups of the phosphoric acid undergo an ester bond a neutral trialkyl ester will be the result, as Eq. (4) shows. 

For a number of reactions of cyclic di- and triesters of phosphoric acid, there are exchange data which can be rationalized on the assumption of trigonal bipyrami-dal intermediates which readily interconvert by pseudorotation. This constitutes a strong argument that at least these cyclic esters react by an associative mechanism and is suggestive evidence that simple trialkyl phosphates also react by this mechanism. The pH dependence of exocyclic versus endocyclic cleavage of methyl ethylene phosphate is readily interpreted in terms of the effect of ionization of the intermediate on the pseudorotation of these pentacoordinate intermediates. ... 

The unsaturated character of these trialkyl esters was shown by the ease with which they were attacked by nitric acid, but still more clearly by the formation, with evolution of heat, of stable crystalline addition compounds when they were mixed with cuprous halides. Thus CuC1.P(OC2H5)3 was described as consisting of colourless crystals melting at 190° to 192° C. and soluble in organic solvents.4 This property they share with phosphine, alkylphosphines and phosphorus trihalides. The phosphoric esters were quite indifferent to cuprous halides. Nor were such addition compounds formed either by phosphorous acid itself or by the dialkyl esters, which may show that the latter compounds have the unsymmetrical formula. Phosphorous acid probably exists in both forms, but first as P(OH)3, i.e. when produced from PC13 and Ha0.5 This may be transformed into the unsym-metrieal form through an addition compound HC1.P(0H)3,4 and probably also exists in the form of complex molecules, such as... 

P(0H)3[HP(0)(0H)2] Phosphorous acid (esters trialkyl phosphite) phosphorige Satire... 

In acidic solution, pliosphate esters are readily cleaved to phosphoric acid. In alkaline solution, however, only trialkyl phosphates, (RO)3PO, are hydrolyzed, and only one alkoxy group is removed. Monoalkyl and dialkyl esters, ROPO(OH)2 and (R0)2P0(0H), are inert to alkali, even on long treatment. This may seem unusual behavior, but it has a perfectly rational explanation. The monoalkyl and dialkyl esters contain acidic —OH groups on phosphorus, and in alkaline solution exist as anions repulsion between like charges prevents attack on these anions by hydroxide ion. 

Synthesis of Phosphoric Acids and their Derivatives. - Among various approaches to phosphate esters the phosphorylation of phenols with dialkyl cyanophosphonate and the synthesis of triaryl phosphates under phase-transfer conditions are worthy of mention. Mixed trialkyl phosphates are also reported to be formed by brief cathodic electrolysis of the reaction of dialkyl phosphonates with aromatic aldehydes and ketones, presumably by rearrangement of the initial a-hydroxy compounds. Further reports have appeared of the generation of metaphosphates by various methods. The synthesis of analogues 1 of famesyl pyrophosphate which incorporate photoactive esters has been reported both compounds are competitive inhibitors of farnesyl transferase. 

Several classes of synthetic oils, such as phosphoric acid esters, polyglycols and silicones, are used as hydraulic lubricants. They are mostly used as fire-resistant lubricants, of importance for coal mines, steel mills and foundries, especially when hydraulic systems operate close to hot areas, e.g. furnaces. Polychlorinated biphenyls, PCBs, are the most fire resistant but are no longer used because of their high and persistent toxicity. Silicones have very poor lubricity and are very expensive, whereas polyglycols with high flash points do not fiilly meet more stringent fire-resistant requirements. At present, therefore, synthetic hydraulic lubricants are almost exclusively based on trialkyl or triaryl phosphates, or their mixtures, available with a wide range of viscosities and adequate low-temperature properties required for hydraulic lubricants. 

Phosphorous acid, H3PO3, is generated by hydrolysis of PCI3 - industrially this is carried out by spraying the chloride into steam at 190 °C. Esters of the acid, both the trialkyl esters [P(OR)3] and the dialkyl esters [(R0)2P(0)H], can be produced directly by substituting the appropriate acid for the water. The esters find much use thus, triphenyl phosphite is most widely used in the manufacture of polyvinyl chloride, while trinonylphenyl phosphite is an excellent stabilizer for the same polymer. 

Reaction of the preceding intermediate mixture with alcohols leads to mixed ester products characterized by high DAP, some trialkyl phosphate, and low MAP content with only traces of phosphoric acid. 

According to D. Swem, phosphate ester can be produced by adopting a-bro-moacid esters and trialkyl phosphoric acid as feeds. The synthetic reaction can be given by the following ... 

A mixed ester of silicic and phosphoric acids appears to be developed after polysilicic acid is extracted as a coacervate from aqueous solution, saturated with salt, into a trialkyl phosphate (171). When first obtained, the triethyl or tributyl phosphate can be dissolved away from silica by another solvent such as benzene. However, when the coacervate is heated under vacuum to remove water, ester inter-... 

Protection of PET from thermal degradation is obtained by removal or deactivation of transesterification catalysts present in PET. Esters of phosphoric acid such as trialkyl or triaryl phosphates can be used for this purpose. Organic phosphites, which are well known to decompose hydroperoxides as secondary antioxidants, are also reported to deactivate metal ions (traces and/or catalyst residues) in polyolefins [4]. In PET, it is suspected that they also deactivate the metal species that catalyse the transesterification reaction. 

---