Orthophosphate reactions

The rates of proton-exchange involving phosphate ions in aqueous solutions enriched with oxygen-17 have been examined by an nmr line-broadening technique . The process appears to be second order in phosphate species and is attributed to the reaction 

At 25 °C, the rate coefficient is 1.45 x 10 l.mole ksec k If diffusion controlled, this rate would be consistent with a transfer in which on average two water molecules bridge the exchanging ions. Using ultrasonic techniques, at the same 

Abnormal dispersion found for concentrations of Na3P04. greater than 0.1 M and at higher pH values, has not been interpreted. Eigen and Schwarz have claimed values of ki and 2 which are higher, by factors of 4 and 2 respectively, than those above. 

Oxygen exchange rates were first examined semiquantitatively , and then more closely, in strong phosphoric acid (e.g. 18.3 Af) , and also in the range pH 0-8.6 . There is a maximum in the rate versus pH curve at pH 5 and a minimum at pH 1 . In order to fit the observations, a three-term rate equation 

Since this study involved pH measurements and acidity constants appropriate to 20 °C, there will be systematic errors in these values. Up to 0.7 M phosphate there was no sign of second-order dependence on its concentration, and thus condensed phosphates are unlikely to be significant. In more concentrated acidic solutions at the same temperature, such condensed phosphates appear highly important , as shown by the rate law 

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L-Ornithine transcarbamoylase catalyzes transfer of the carbamoyl group of carbamoyl phosphate to ornithine, forming citrulline and orthophosphate (reaction 2, Figure 29-9). While the reaction occurs in the mitochondrial matrix, both the formation of ornithine and the subsequent metabolism of citmlline take place in the cytosol. Entry of ornithine into mitochondria... 

Novak, L. T., and Adriano, D. C. (1975). Phosphorus movement in soils-. Soil-orthophosphate reaction kinetics. J. Environ. Qual. 4, 261-266. 

As shown in these reactions, the phosphorus must be in the phosphate form. The reaction occurs in water, so the phosphate ion originates a series of equilibrium orthophosphate reactions with the hydrogen ion. This series is shown as follows (Snoeyink and Jenkins) ... 

Chapter IV. a-Chloromethylnaphthalene (IV,23) benzylamine (Gabriel synthesis) (IV,39) i r.N -dialkylanilines (from amines and trialkyl orthophosphates) (IV,42) a-naphthaldehyde (Sommelet reaction) (IV,120) a-phenyl-cinnamic acid (Perkin reaction using triethylamine) (IV,124) p-nitrostyrene (IV,129) p-bromonaphthalene and p naphthoic acid (from 2 naphthylamine-1 -sulphonic acid) (IV,62 and IV,164) diphenic acid (from phenanthrene) (IV,165). 

Nickel Phosphate. Tri nickel orthophosphate [14396-43-17, Ni2(P0 2 7H20, exists as apple-green plates which decompose upon heating. It is prepared by the reaction of nickel carbonate and hot dilute phosphoric acid. Nickel phosphate is an additive to control the crystal size of ziac phosphate ia coaversioa coatiags which are appHed to steel prior to its being paiated (see Metal surface treatments). 

Pyrophosphates. The simplest linear condensed phosphates are pyrophosphates, which can be considered as the dehydration product of two orthophosphate groups. A water molecule is eliniinated to form a P—O—P linkage in a reversible reaction. 

Alkali Meta.IPhospha.tes, A significant proportion of the phosphoric acid consumed in the manufacture of industrial, food, and pharmaceutical phosphates in the United States is used for the production of sodium salts. Alkali metal orthophosphates generally exhibit congment solubility and are therefore usually manufactured by either crystallisation from solution or drying of the entire reaction mass. Alkaline-earth and other phosphate salts of polyvalent cations typically exhibit incongment solubility and are prepared either by precipitation from solution having a metal oxide/P20 ratio considerably lower than that of the product, or by drying a solution or slurry with the proper metal oxide/P20 ratio. 

Titanium Phosphorous Containing Chelates. The reaction of a mixture of mono (alkyl) diacid orthophosphate, di(alkyl)monoacid orthophosphate, and TiCl in a high boiling hydrocarbon solvent such as heptane, with nitrogen-assisted evolution of Hberated HCl, gives a mixture of titanium tetra(mixed alkylphosphate)esters, (H0)(R0)0=P0) Ti(0P=0(0R)2)4 in heptane solution (100). A similar mixture can be prepared by the addition of two moles of P2O5 to mole of TiCl in the presence of six moles of alcohol ... 

NOTE As the reaction between calcium and orthophosphate is rapid, it is not generally advisable to add phosphate to the feedline at any great distance from the boiler because the precipitation of phosphate sludge may foul the line quickly and eventually cause a complete blockage. 

Alternatively, sodium metaphosphate (an orthophosphate that has been molecularly dehydrated by the removal of a molecule of water) may be employed because this must regain the lost water molecule before reacting with calcium as the orthophosphate. This delay may provide the time necessary to ensure that the precipitation reaction takes place solely within the confines of the bulk BW. 

The first example of a tetrakisimido analogue of the orthophosphate ion, PO, the solvent-separated ion pair [(THF)4Li][(THF)4Li2P(Nnaph)4] (16), was reported by Russell et al. [21]. This complex was isolated in low yield from the reaction of P2I4 with a-naphthylamine in THF/NEt3, followed by the addition of "BuLi. The mechanism of this remarkable redox process is not understood. 

Condensation of CO2, ammonia, and ATP to form carbamoyl phosphate is catalyzed by mitochondrial carbamoyl phosphate synthase I (reaction 1, Figure 29-9). A cytosolic form of this enzyme, carbamoyl phosphate synthase II, uses glutamine rather than ammonia as the nitrogen donor and functions in pyrimidine biosynthesis (see Chapter 34). Carbamoyl phosphate synthase I, the rate-hmiting enzyme of the urea cycle, is active only in the presence of its allosteric activator JV-acetylglutamate, which enhances the affinity of the synthase for ATP. Formation of carbamoyl phosphate requires 2 mol of ATP, one of which serves as a phosphate donor. Conversion of the second ATP to AMP and pyrophosphate, coupled to the hydrolysis of pyrophosphate to orthophosphate, provides the driving... 

If barium orthophosphate is formed in this manner, we cem guarantee that the final solid state reaction product will consist of 100% of the desired product. 

A. Inositol Phosphates.—Phosphatidyl inositol (71) is hydrolysed in mammalian tissues to wyo-inositol 1,2-cyclic phosphate (72).i myoinositol 1-phosphate (73) is released simultaneously but is not converted into (72) by the enzyme system. Periodate oxidation of (73) liberates orthophosphate quantitatively, the unstable dialdehyde phosphate (74) being an intermediate. Little or no orthophosphate is released from glucose 6-phosphate under the same oxidative conditions, and this reaction has been used to assay (73). 

Crisp et al. (1978) were able to follow the course of the cement-forming reaction using infrared spectroscopy and to confirm previous observations. They found that the technique could be used to distinguish between crystalline and amorphous phases of the cement. Hopeite shows a number of bands between 1105 and 1000 cm this multiplicity has been explained by postulating a distortion of the tetrahedral orthophosphate anion. (Two-thirds of the zinc ions are tetrahedrally coordinated to four phosphate ions, and the remainder are octahedrally coordinated to two phosphate and four water ligands.)... 

They considered that cement formation was the result of an acid-base reaction leading to the formation of hydrates by a through-solution mechanism, by nucleation and precipitation from pore fluids. Two phases were found in the matrix, one amorphous and the other crystalline. The crystalline phase was newberyite. Finch Sharp concluded that the amorphous phase was a hydrated form of aluminium orthophosphate, AIPO4, which almost certainly contained magnesiiun. They ruled out a pure AlP04.nH20, for they considered that the reaction could not be represented by the equation... 

Finch, T. Sharp, J. H. (1989). Chemical reactions between magnesia and aluminium orthophosphate to form magnesia-phosphate cements. Journal of Materials Science, 24, 4379-86. 

The most general method for the simultaneous analysis of oxyanions by gas chromatography is the formation of trimethylsilyl derivatives. Trimethylsilyl derivatives of silicate, carbonate, oxalate, borate, phosphite, phosphate, orthophosphate, arsenite, arsenate, sulfate and vanadate, usually as their ammonium salts, are readily prepared by reaction with BSTFA-TMCS (99 1). Fluoride can be derivatized in aqueous solution with triethylchlorosilane and the triethylfluorosilane formed extracted into an immiscible organic solvent for analysis by gas chromatography [685). 

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