Phosphorus trialkyl phosphates

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. ... 

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. 

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). 

The reaction of a trialkyl phosphate with an alkyl halide to produce an alkyl phosphonate. The first step involves nucleophilic attack by the phosphorus on the alkyl halide, followed by the halide ion dealkylation of the resulting trialkoxyphosphonium salt. 

Although quantitative yields of chloroform were found, low yields of trialkyl phosphite were produced and these decreased with time as the yields of trialkyl phosphate and dialkyl phosphate increased, e.g. in the reaction of sodium n-butoxide (0.06 mol) with phosphorus (0.009 mol) in 30 ml of methanol and 50 ml of n-butanol 47% of phosphite was produced in 3 h. together with 19% of phosphate and 7% of phosphonate. The product composition changed to 34%, 22% abd 21% respectively after 7 h. 

Oxygen, sulfur, and selenium will add to the phosphorus atom to give compounds known as trialkyl phosphates, trialkyl thiophosphates, or trialkyl selenophosphates, respectively, as illustrated by the following equations ... 

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. 

Trialkyl phosphates are manufactured by reacting phosphorus(V) oxychloride with excess alcohol, in particular ethanol, butanol, isobutanol and 2-ethylhexanol ... 

Electrolysis of a stirred suspension of red phosphorus in alcohol with graphite electrodes and with continous introduction of gaseous HCl gave trialkyl-phosphates and RCl. The following current yields were reported... 

The majority of newly reported nucleoside 5 -monophosphates have been prepared using phosphorus oxychloride in trialkyl phosphate solution. These include the monophosphates of 2-fluoroadenosine, 2-amino-6-chloro-9-(/S-D-ribofuranosyl)-purine, bredinin (6), cordycepin 2 -azido-2 -deoxyadenosine, 2 -fluoro-... 

With phthalic anhydride and trialkyl phosphites, the reaction takes V an entirely different course, the main products being biphthalyl (70%) and trialkyl phosphate. It was suggested that the phosphorus atom of a phosphite ester attacks the oxygen of the anhydride carbonyl, forming an intermediate which undergoes valency expansion to generate in this unique instance a carbene and a phosphate ester (276). Dimerization of this resonance-stabilized carbene w ould furnish the product. 

Two highly unusual procedures for the preparation of trialkyl phosphates have been described. In the first, alkanes are made to react with trimethyl phosphite in a medium consisting of FeCl2.4H2O Zn(0) O2 in pyridine - acetic acid. The essential reaction appears to be one of Fe(II)-catalysed oxidation of the tervalent phosphorus ester by an alkyl hydroperoxide to afford an alkyl dimethyl phosphate. In the second procedure, described in considerable detciil, a Cu(II) catalyst aids in the interaction of red... 

More usually, the plasticizer component of the formulation is replaced by flame-retardant plasticizers such as liquid chlorinated paraffins, acting as secondary plasticizers up to 30 per cent of the original plasticizer content. As an associate plasticizer, phosphoric esters are often used. The appropriate flame-retardance is achieved by adding 1 or 2 phr. of phosphorus to the compound. More rigid or more flexible cold-resistant products can be formulated with triaryl or trialkyl phosphates, respectively. Halogenated phosphates may also reduce the flammability of plasticized PVC. 

If high pnrity is essential, DAPs can be prepared by the oxidation of the corresponding dialkyl phosphite [67], which is in turn prepared from phosphorus trichloride. To avoid phosphorus halides, a phosphation reagent can be prepared from the reaction of Iowa trialkyl phosphates with phosphoric anhydride, yielding a range of intermediates, depending on the conditions and molar ratio [68]. 

Insertion of Phosphorus Pentoxide into a Phosphate, Followed by Epoxide Insertion. The insertion of phosphorus pentoxide into a trialkyl phosphate or a tris(haloalkyl) phosphate produces oligomeric metaphosphoric anhydrides, which upon further insertion of an epoxide into the P—0—P linkages affords oligomeric phosphates. An older route for the chloroethyl phosphate oligomers used a transalkylation reaction for polycondensation, producing dichloroethane as by-product. 

Phosphorus(V) from phosphorus(lll) compounds. Tribulylphosphine added at 25° under Ng during 30 min. with water-cooling to N,N-diethyl-2,2,2-trichloro-acetamide, and kept an additional 4 hrs. at 50-55° N,N-diethyl-l,2,2-trichloro-vinylamine (startg. m. f. 442) (Y 82.5%) and tri-n-butylphosphine oxide (Y 72.6%).—This new reaction appears to be general for tert. phosphines and trialkyl phosphites. It also represents a novel method for the prepn. of a new class of vinylamines. F. e., also with trialkyl phosphites, which are oxidized to trialkyl phosphates, s. A. J. Speziale and R. G. Freeman, Am. Soc. 82, 903 (1960). 

Phosphorylation. Phosphorus oxychloride reacts with alcohols, amines, and thiols, resulting in phosphorylation of these functional groups. Trimethyl phosphate is a particularly effective solvent, and tertiary amine bases are generally used as well. Treatment of primary alcohols with POCI3 results in the formation of phosphonyl dichloride intermediates which, in the presence of excess alcohol, convert to symmetrical trialkyl phosphates. It is generally possible to isolate aryl phosphorodichloridates when a two-fold excess of (1) is used and AICI3, KCl, or pyridine is used as a catalyst. Secondary and tertiary alcohols tend to form alkyl chlorides and phosphoric acid. 

This explanation for the P chemical-shift variation based on bond-angle differences could also explain the results shown in Table I. As the alkyl group in the series of trialkyl phosphates gets bulkier, hence as the ester (R)OPO(R) bond angle gets larger, the phosphorus atom is more shielded. 

Organophosphate Ester Hydraulic Fluids. Organophosphate esters are made by condensing an alcohol (aryl or alkyl) with phosphorus oxychloride in the presence of a metal catalyst (Muir 1984) to produce trialkyl, tri(alkyl/aryl), or triaryl phosphates. For the aryl phosphates, phenol or mixtures of alkylated phenols (e.g., isobutylated phenol, a mixture of several /-butylphenols) are used as the starting alcohols to produce potentially very complex mixtures of organophosphate esters. Some phosphate esters (e.g., tricresyl and trixylyl phosphates) are made from phenolic mixtures such as cresylic acid, which is a complex mixture of many phenolic compounds. The composition of these phenols varies with the source of the cresylic acid, as does the resultant phosphate ester. The phosphate esters manufactured from alkylated phenylated phenols are expected to have less batch-to-batch variations than the cresylic acid derived phosphate esters. The differences in physical properties between different manufacturers of the same phosphate ester are expected to be larger than batch-to-batch variations within one manufacturer. 

In spite of many previous studies on the mechanisms by which trialkyl phosphites interact with a -halogenocarbonyl compounds, the reactive intermediates which lead to ketophosphonate (Arbuzov reaction) and to vinyl phosphate (Perkow reaction) have in no cases been clearly identified. It is generally believed (JL), however, that the Arbuzov product 4 results from initial attack by phosphorus at the cf-carbon atom, whereas the Perkow product 7 is formed by initial attack at the carbonyl carbon atom, followed by migration of phosphorus from carbon to oxygen (Scheme 1). 

A novel and versatile synthesis of dialkyl steroid phosphates employs the steroidal alkoxyl radical (545), generated by photolysis of the corresponding nitrite. In the presence of a trialkyl phosphite, the radical attacks at phosphorus to give a phosphoranyl radical (546), which loses one of its four alkyl groups to give the desired phosphate (547). The preference for expulsion of one of the small alkyl groups, rather than the steroidal moiety, is thought to be determined by... 

A similar oxidation of trivalent phosphorus to pentavalent phosphorus occurs in trialkyl or triaryl phosphites. Triphenyl phosphite is converted by ozone in dichloromethane at 5-10 C into triphenyl phosphate in 95% yield [775] and by argentic oxide in 30% yield [557] (equation 538). 

The neutral phosphonate esters, D(EB)[(EB)P], D(4-MPe-2)[BP], D(4-MPe-2)[(iB)P] and D(4-MPe-2)[PP] were prepared by the Michaelis-Arbuzov Reaction in which alkyl halides were reacted with previously prepared trialkyl phosphites. The neutral phosphate, T(4-MPe-2)P, was prepared by a conventional esterification method in which 4-methyl-2-pentanol was reacted with POCI3 in the presence of pyridine. The temperature during the reaction was kept below 15°C to prevent disproportionation of the alkyl group. The neutral phosphinate ester, B[DBP], was prepared by esterification of dibutyl phosphorus oxychloride, (C Hg)2P0C1, in the presence of pyridine. 

At low temperatures, trialkyl phosphites and chloral give the 1,4,2-dioxaphos-pholans (96), which decompose above —10 °C to give the vinyl phosphates (97). 1,4,2-Dioxaphospholans are also formed from benzaldehyde and the tervalent phosphorus compounds (98). ... 

A novel procedure has been developed for the synthesis of phosphate esters of hindered alcohols, and was designed to avoid nucleophilic displacement reactions. It involves photolysis of the alkyl nitrite in the presence of a trialkyl phosphite and proceeds by addition of the alkoxyl radical to phosphorus followed by elimination of an alkyl group (Scheme 3). ... 

The reaction of epoxides or episulfides with trialkyl phosphites containing one or more secondary or tertiary alkyl groups is reported to give mainly phosphonates rather than olefins and phosphates (287). Evidently, in this case nucleophilic attack of the phosphorus reagent on carbon takes place. 

It has already been indicated that the course of any reaction may depend, to some extent, on the nature of the phosphite (or phosphonite) ester (phosphinite esters yield phosphine oxides). Thus, tris(perfluoroalkyl) phosphites do not undergo a Michaelis-Arbuzov reaction with perfluoroiodoalkanes, although reports on the outcome of any reaction between triethyl phosphite and CF3I, under normal conditions, are conflicting reactions do appear to proceed under photostimulation. A normal reaction does take place at high temperatures between polyfluorinated trialkyl phosphites and methyl iodide, when the product, MeP(0)(0Rf)2, is accompanied by oxidation of the phosphite to phosphate Either elimination or alkylation accompanies the formation of unidentified phosphorus-containing products in the reactions between trialkyl phosphites and the halides Cl3C(CF2) Cl n - 2, 4 or 6) ... 

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