Metaphosphate works

The reaction of 151 with methanol to give dimethyl phosphate (154) or with N-methylaniline to form the phosphoramidate 155 and (presumably) the pyrophosphate 156 complies with expectations. The formation of dimethyl phosphate does not constitute, however, reliable evidence for the formation of intermediate 151 since methanol can also react with polymeric metaphosphates to give dimethyl phosphate. On the other hand, reaction of polyphosphates with N-methylaniline to give 156 can be ruled out (control experiments). The formation of 156 might encourage speculations whether the reaction with N,N-diethylaniline might involve initial preferential reaction of monomeric methyl metaphosphate via interaction with the nitrogen lone pair to form a phosphoric ester amide which is cleaved to phosphates or pyrophosphates on subsequent work-up (water, methanol). Such a reaction route would at least explain the low extent of electrophilic aromatic substitution by methyl metaphosphate. 

Whey protein concentrates (WPC), which are relatively new forms of milk protein products available for emulsification uses, have also been studied (4,28,29). WPC products prepared by gel filtration, ultrafiltration, metaphosphate precipitation and carboxymethyl cellulose precipitation all exhibited inferior emulsification properties compared to caseinate, both in model systems and in a simulated whipped topping formulation (2. However, additional work is proceeding on this topic and it is expected that WPC will be found to be capable of providing reasonable functionality in the emulsification area, especially if proper processing conditions are followed to minimize protein denaturation during their production. Such adverse effects on the functionality of WPC are undoubtedly due to their Irreversible interaction during heating processes which impair their ability to dissociate and unfold at the emulsion interface in order to function as an emulsifier (22). 

These introductory remarks will have a twofold objective first, to review the history of the field, in an attempt to put the following papers into prospective second, to present some work from my own laboratory on a possible biomimetic system—the generation of monomeric metaphosphate, and its reactions that seem to parallel the action of pyruvate kinase and of amidotransferases. 

Arnold Satterthwait (73), continuing that work, also has prepared what appears to be monomeric methyl metaphosphate in solution. His preparative method utilizes the Conant-Swan fragmentation of /3-halophosphonates (Equation 8). The material reacts with substi-... 

Reactions of phosphate monoester dianions and of phosphorylated pyridines with water and other nucleophiles proceed through a mechanism that shows many of the characteristics expected for reaction through an intermediate metaphosphate monoanion, and several investigators (3-5) have suggested that these and related reactions proceed through such an intermediate. However, recent work has shown that metaphosphate, if it is formed, has too short a lifetime in several hydroxylic solvents to diffuse through the solvent before reaction, so that the reaction must occur by a stepwise or concerted preassociation mechanism. Methanolysis of the 2,4-dinitrophenyl phosphate dianion occurs with inversion, for example (6). 

There is no correlation " between substances entered into melt and those really existing in it. E.g., potassium nitrate and nitrite are decomposed to K2O at temperatures considerably lower flian flie temperature of the experiment (700"C). Ditto referred to K2S2O7 and Na2S20g as acidic phosphates. " In the latter work it has been found that pyrophosphate acidity is larger than that for metaphosphate. However, titration of phosphorus (V) oxo-compounds in melts runs according to the scheme [10.4.39], The acidity decreases. 

Of the esters, starch phosphate is produced by reaction with phosphorus oxychloride, polyphosphates, or metaphosphates a cross-bonded product results. Total degree of substitution is determined by measuring the phosphorus content, and the mono- to disubstitution ratio can be calculated by potentio-metric titration. Allowance is made for the natural phosphorus content of the starch. Treatment of starch with acetic anhydride produces starch acetate, which has improved paste stability over native starch. The acetyl group is very labile, and hydrolyses readily under mild alkaline conditions. When a known amount of alkali is used, the excess can be titrated and the ester function measured. This is not specific, however, and a method based on an enzymatic measurement of the acetate has been developed in an ISO work group. The modified starch is hydrolyzed under acidic conditions, which releases acetic acid and permits filtration of the resulting solution. Acetic acid is then measured by a commercially available enzyme test kit. Both bound and free acetyl groups can be measured, and the method is applicable... 

For several years TVA produced calcium metaphosphate, Ca(POs)2, in a demonstration-scale plant. The process consisted of burning elemental phosphorus and reacting the resulting P2O5 vapor with phosphate rock. The molten product was tapped out of the ftirnace and -solidified on a watei cooled steel drum [17]. The resulting vitreous flakes were cooled further and crushed to pass a 10-mesh screen (about 1.6 mm). Development of a process for production of calcium metaphosphate involved three pilot plants and three demonstration-scale plants and a considerable amount of laboratory- and bench-scale work [IS]. The third demonstration-scale plant was technically successful and operated about 16 years, starting in 1949. A total of nearly 1 miflion tonnes was produced, including relatively small amounts from the first and second demonstration-scale plants. The process was economically competitive with TSP when both products were based on elemental phosphorus made by the electric-furnace process. 

The detailed chemistry of these films is stiU controversial older works based on elemental analysis with SEM-EDX showed that the film contained Zn, S, P, C and O [14]. XPS [15] and AES [16,17] have also been used to provide chemical differentiation for the different elements P was claimed to be present as a phosphate and S as a sulfide, the corresponding cation being zinc or iron. XANES spectroscopy revealed that the chemical nature of P and S in the tribofikns was different from that of the pure ZnDTP substances and depends on the alkyl group used in ZnDTP [18]. With isopropyl ZnDTP, phosphorus is found to correspond closely to metaphosphate (polyphosphate with a cyclic structure) whereas with u-butyl ZnDTP pyrophosphates are found. This is important when discussing the results obtained from commercial ZnDTP, which often consist of a blend of ZnDTP molecules containing different alkyl groups [3]. 

In 1963, Caton and Freund (75) made preliminary voltammetric studies of a number of redox systems in molten alkali metal metaphosphates, but the work was limited by the lack of a reference electrode. In 1971 Wolfe and Caton (76) devised a silver reference electrode which was applied to potentiometric and chronopotentiometric studies in equimolar mixtures of sodium and potassium metaphosphates at 700 C of several redox couples. Diffusion coefficients and standard potentials were evaluated. 

Until fairly recently, the monomeric metaphosphate ion (POg ) was assumed not to exist. Now, however, important work has provided evidence that the metaphosphate ion, which is analogous to NO, may be an important intermediate in the hydrolysis of bioorganic phosphate esters. 

When sodium acid metaphosphate was first discovered, one form of [Na2H(P03)3]n salt was extremely easy to crystallize as a pure compound. After some initial work was completed, I decided that the remainder of this system should be explored. Three more new salts were discovered, but the initial supply of the first discovered salt had become exhausted. 

It should be noted that calcium polyphosphates are often called metaphosphates in the literature and patents, if they have M2O-P2O5 ratios near unity. Throughout this work, the word metaphosphate will be reserved for ring phosphates while chain phosphates will be named polyphosphates. In most modern usage the prefix poly- has unfortunately been dropped from a name. Calcium tripolyphosphate, Ca5(P30io)2, is named calcium triphosphate, which can easily be confused with tricalcium phosphate, Ca3(P04)2, an orthophosphate, by those who only occasionally engage in phosphate chemistry. In this work polyphosphates shall be named polyphosphates, unless reference is made to work where polyphosphates are named without the prefix. Here, they will be named as in the cited literature. 

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