Trialkyl phosphates

Formation of esters of inorganic acids (Section 15 9) Alkyl nitrates dialkyl sulfates trialkyl phos phites and trialkyl phosphates are examples of alkyl esters of inor game acids In some cases these compounds are prepared by the direct reaction of an alcohol and the inorganic acid... 

The purification of the galHum salt solutions is carried out by solvent extraction and/or by ion exchange. The most effective extractants are dialkyl-phosphates in sulfate medium and ethers, ketones (qv), alcohols, and trialkyl-phosphates in chloride medium. Electrorefining, ie, anodic dissolution and simultaneous cathodic deposition, is also used to purify metallic galHum. 

Inefficiencies ia the reaction with POCl leads to alternative production of trialkyl phosphates by employing the sodium alkoxide rather than the alkyl alcohol itself Dialkyl aryl phosphates are produced ia two steps. The low molecular weight alcohol iavolved (eg, butyl) first reacts with excess POCl. The neutral phosphate ester is then completed by the iatermediate chloridate reacting with excess sodium arylate ia water. 

Most of the phosphate esters are used in the production of hydrauHc fluids (qv), plastic and elastomer additives, flame retardants (qv), oil stabilizers, pesticides (qv), and medicinal intermediates (see Surfactants). Some trialkyl phosphates, OP(OR)2, are outstanding solvents for nitrates, especially (UO2) (N02)2, and therefore are important in uranium processing (see Extraction). 

Dialkylphosphorochloridates, (R0)2P(=0)C1, react with trialkyl phosphate esters to give organic pyrophosphates. Organopyrophosphates are anticholinesterase agents and should be handled with great caution (16). Atropine sulfate is a specific antidote. 

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). 

Curious products isolated by Bailey and Evans from the reaction of benzotrisfuroxan with triphenyl phosphine have been examined by X-ray crystallography by Cameron and Prout. The structures (44-46) were determined.A molecular complex of trialkyl phosphate with benzotrisfurazan is formed using a trialkyl phosphite as reducing agent. 

An antipolymerization agent such as hydroquinone may be added to the reaction mixture to inhibit the polymerization of the maleate or fumarate compound under the reaction conditions. This reaction is preferably carried out at a temperature within the range of 20°C to 150°C. This reaction is preferably carried out at atmospheric pressure. Reaction time of 16 to 24 hours have bean specified for this reaction by J.T. Cassaday. The reaction is preferably carried out in a solvent such as the low molecular weight aliphatic monohydric alcohols, ketones, aliphatic esters, aromatic hydrocarbons or trialkyl phosphates. 

Triethyl phosphite can be obtained from Virginia Carolina Chemical Corp., Eastman Kodak Co., Aldrich Chemical Co., K and K Laboratories, and Matheson, Coleman and Bell. The presence of dialkyl hydrogen phosphite or trialkyl phosphate is not deleterious, but a correction for assay is required. Fractionation readily separates triethyl phosphite (b.p. 48-49°/ll mm.) from diethyl hydrogen phosphite (b.p. 72°/ll mm.) and triethyl phosphate (b.p. 90°/10 mm.). The presence of amines and amine hydrochlorides may seriously interfere with the alkylation, especially in the case of trimethyl phosphite (see Table I). The checkers redistilled triethyl phosphite obtained from Matheson, Coleman and Bell. 

Trialkyl phosphates form volatile 1 1 adducts with acids such as nitric and chloroacetic, from which the esters are recovered by base treatment. I.r. and n.m.r. spectral data suggest that these are hydrogen-bonded complexes. At low temperatures, in FSOaH-SbFj, trialkyl phosphates were shown (by n.m.r.) to give protonated species in which there appears to be considerable pir-d-rr back-donation from oxygen to phosphorus. These species are not stable the tri-n-butyl ester decomposing over the course of two days to MeaC+ and (HOiP. ... 

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. ... 

Studies with rats treated orally with triaryl or trialkyl phosphate esters (which may be found in organophosphate ester hydraulic fluids) indicate that these compounds and their metabolites are readily excreted in the urine, bile, feces and, to a limited extent, in expired air (Kurebayashi et al. 1985 Somkuti and Abou-Donia 1990a Suzuki et al. 1984a Yang et al. 1990). Urinary excretion of metabolites appears to be the predominant elimination route in rats for tri-ort/zo-cresyl phosphate and tri-para-cresyl phosphate, but biliary excretion of parent material and metabolites is also important (Kurebayashi et al. 1985 NTP... 

Product description Trialkyl phosphate Mixed triaryl phosphate Phosphate ester mixture... 

The first commercial trialkyl phosphate esters (TAP) were tricresyl phosphate (TCP) and trixylenyl phosphate (TXP), referred to as "natural" phosphate esters because the cresols and xylenols used as raw materials are derived from petroleum oil or coal tar (Marino and Placek 1994). These products are not commercially significant at present however, at waste disposal sites, contaminants from older product formulations may be encountered, particularly those containing the neurotoxic tri-o/T/io-cresyl phosphate isomer. "Synthetic" phosphate esters are derived from synthetic feedstocks. Specific synthetic reactions have been developed to produce triaryl, trialkyl, and alkyl Aryl esters. The triaryl phosphates are currently... 

It is now known1 that trialkyl phosphates will indeed alkylate phenols. The idea has been extended2 to the production of methyl ethers from alcohols and trimethyl phosphate, and of a butyl ether according to the equation... 

Tertiary amines can often be formed by the reaction between a trialkyl phosphate on an amine3 at a high temperature ... 

The catalysed two-phase adaptation of the Atherton-Todd procedure is effective for the phosphorylation of primary alcohols and of phenols [6] to produce trialkyl phosphates and dialkyl aryl phosphates. Trialkyl phosphates have also be obtained in high yield (>75%) from the alkylation of preformed tctra-n-butylammonium di-/-butylphosphate [7], Subsequent cleavage of the /-butyl groups provide a simple synthesis of monoalkyl phosphates. 

Potentially tautomeric pyrimidines and purines are /V-alkylated under two-phase conditions, using tetra-n-butylammonium bromide or Aliquat as the catalyst [75-77], Alkylation of, for example, uracil, thiamine, and cytosine yield the 1-mono-and 1,3-dialkylated derivatives [77-81]. Theobromine and other xanthines are alkylated at N1 and/or at N3, but adenine is preferentially alkylated at N9 (70-80%), with smaller amounts of the N3-alkylated derivative (20-25%), under the basic two-phase conditions [76]. These observations should be compared with the preferential alkylation at N3 under neutral conditions. The procedure is of importance in the derivatization of nucleic acids and it has been developed for the /V-alkylation of nucleosides and nucleotides using haloalkanes or trialkyl phosphates in the presence of tetra-n-butylammonium fluoride [80], Under analogous conditions, pyrimidine nucleosides are O-acylated [79]. The catalysed alkylation reactions have been extended to the glycosidation of pyrrolo[2,3-r/]pyrimidines, pyrrolo[3,2-c]pyridines, and pyrazolo[3,4-r/]pyrimidines (e.g. Scheme 5.20) [e.g. 82-88] as a route to potentially biologically active azapurine analogues. 

The use of trialkyl phosphates for dialkylation of anilines has been found applicable to naphthylamines and to a large number of anilines substituted in the ortho, meta, or para position by groups such as chloro, methoxy, and methyl and in the meta position by fluoroalkyl (author s laboratory). The reaction has been used to introduce ethyl and M-butyl as well as methyl groups by employing the appropriate phosphate esters. The reported yields range from 50% to 95%. 

Trialkyl phosphites react rapidly with oxygen, particularly in the presence of radical sources, to yield trialkyl phosphates. Results of several studies are consistent with a sequence first proposed by Walling and Rabinowitz (24),... 

Because of the lack of information in the literature on the radical reactions of compounds of quinquevalent phosphorus, it is impossible to postulate a readily acceptable mechanism for the oxidation of zinc dialkyl dithiophosphates. Colclough and Cunneen (7) rejected immediately the possibility of hydrogen abstraction, but in view of the present results serious consideration has been given to this reaction. During this work it was shown (15) that abstraction of hydrogen from trialkyl phosphates, trialkyl phosphonates, and sodium dialkyl phosphates can occur at room temperature in an aqueous medium in the presence of hydroxy radicals. 

Phosphates have been formed by slow hydrolysis of trialkyl phosphates, hydrogen phosphate ions, or metaphosphoric acid, which liberate phosphate ions (see p. 46 in Ref. 31). This may be of interest as a precursor for the preparation of phosphide semiconductors. 

Problem 13.60 Explain why trialkyl phosphates are readily hydrolyzed with OH to dialkyl phosphate salts, whereas dialkyl hydrogen phosphates and alkyl dihydrogen phosphates resist alkaline hydrolysis. 

Mannitol hexanitrate is obtained by nitration of mannitol with mixed nitric and sulfuric acids. Similarly, nitration of sorbitol using mixed acid produces the hexanitrate when the reaction is conducted at 0—3°C and at —10 to —75°C, the main product is sorbitol pentanitrate (117). Xylitol, ribitol, and L-arabinitol are converted to the pentanitrates by fuming nitric acid and acetic anhydride (118). Phosphate esters of sugar alcohols are obtained by the action of phosphorus oxychloride (119) and by alcoholysis of organic phosphates (120). The 1,6-dibenzene sulfonate of D-mannitol is obtained by the action of benzene sulfonyl chloride in pyridine at 0°C (121). To obtain 1,6-dimethanesulfonyl-D-mannitol free from anhydrides and other by-products, after similar sulfonation with methane sulfonyl chloride and pyridine the remaining hydroxyl groups are acetylated with acetic anhydride and the insoluble acetyl derivative is separated, followed by deacetylation with hydrogen chloride in methanol (122). Alkyl sulfate esters of polyhydric alcohols result from the action of sulfur trioxide—trialkyl phosphates as in the reaction of sorbitol at 34—40°C with sulfur trioxide—triethyl phosphate to form sorbitol hexa(ethylsulfate) (123). 

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