Phosphoric acid, preparation crystalline

Tricalcium phosphate, Ca2(P0 2> is formed under high temperatures and is unstable toward reaction with moisture below 100°C. The high temperature mineral whidockite [64418-26-4] although often described as P-tricalcium phosphate, is not pure. Whidockite contains small amounts of iron and magnesium. Commercial tricalcium phosphate prepared by the reaction of phosphoric acid and a hydrated lime slurry consists of amorphous or poody crystalline basic calcium phosphates close to the hydroxyapatite composition and has a Ca/P ratio of approximately 3 2. Because this mole ratio can vary widely (1.3—2.0), free lime, calcium hydroxide, and dicalcium phosphate may be present in variable proportion. The highly insoluble basic calcium phosphates precipitate as fine particles, mosdy less than a few micrometers in diameter. The surface area of precipitated hydroxyapatite is approximately... 

The corresponding phosphoryl and thiophos-phoryl pseudohalides are also known, i.e. P0(NC0)3, PS(NC0)3, etc. Preparations are by standard procedures such as those on the diagram for PCI3 (p. 497). As indicated there, P(CN)3 has also been made it is a highly reactive white crystalline solid mp 203° which reacts violently with water to give mainly phosphorous acid and HCN. 

All these steps proceed to afford free or N -substituted crystalline cytidines 6 in high yields [11] (cf. the preparation of N (tetramethylene)cytidine 6b in 95.4% yield in Section 1.1.). This simple one-pot reaction is also very easy to perform on a technical scale, as are the subsequently discussed analogous silylation-aminations of purine nucleosides and other hydroxy-N-heterocycles (cf. Sections 4.2.4 and 4.2.5). The concept of silylation-activation while simultaneously protecting hydroxyl groups in alcohols, phenols, or phosphoric acids by silylation was subsequently rediscovered and appropriately termed transient protection [16-18]. 

Isomers of D-apiofuranosyl 1-phosphate have been prepared by treating a mixture of jS-o-apio-D-furanosyl and /3-D-apio-L-furanosyl tetra-acetates with crystalline phosphoric acid. a-o-Apio-o- (59) and a-o-apio-L-furanosyl-1-phosphate (60) and their cyclic phosphates were separated by chromatography and identified by H n.m.r. o-Apiose is metabolized in parsley and Lemna minor with the possible formation of UDP-D-apiose. L. minor will convert UDP-a-glucuronic acid into a-o-apio-D-furanosyl-1,2-cyclic phosphate (61) but no evidence of UDP-o-apiose was found, although it is possible that (61) arose from the rapid hydrolysis of UDP-o-apiose. 

Crystalline phosphoric acid has also been used to prepare sugar diphosphates, e.g. a-D-ribose 1,5-diphosphate (62) and hexose 1,6-diphosphates. 

Anhydro-D-dulcitol (XXXV) has been prepared by a method which demonstrates its structure. Hockett and coworkers11 prepared it from methyl 3,6-anhydro-a-D-galactopyranoside but both the anhydride itself and its tetraacetate were liquid. Carr63 obtained another anhydro derivative of dulcitol by heating it with phosphoric acid. This also was a liquid but gave rise to a crystalline dibenzoate and a dicarbanilate and was a dianhydro derivative, but no constitutional studies have yet been carried out on this substance. 

Addition of a soluble Zr(IV) salt to phosphoric acid results in the precipitation of a gelatinous amorphous solid. The stoichiometric crystalline zirconium phosphate can be prepared by refluxing zirconium phosphate-gel in concentrated phosphoric acid [5]. The procedures for synthesis of zirconium phosphate have been described in detail elsewhere [6]. 

Anhydrous dipotassium hydrophosphate, K2HPO4, could not be obtained by T. Graham in the solid crystalline condition L. Staudenmaier always obtained a more acid phosphate by crystallization from soln. containing eq. quantities of potassium hydroxide or carbonate and phosphoric acid. No hydrated form has been prepared. E. G. Parker, and J. d Ans and O. Schreiner have studied the conditions under which potassium and sodium salts are formed as solid phases— vide Figs. 86 and 87. E. von Berg prepared dirubidium hydrophosphate,... 

Rhombic ny.sl.als. or white crystalline powder, easily soluble iti water. Its principal asc is in the preparation of magnesia mixture, for the determination of phosphoric acid. 

Another preparative method in which the rate of precipitation is slow involves slow decomposition of zirconium fluoro complexes [14], These are first prepared by adding an appropriate amount of hydrofluoric acid (HF) to the zirconyl salt and these complexes are decomposed in the presence of phosphoric acid, with a slow stream of nitrogen or water vapor passing through the system. The rate of precipitation of zirconium phosphate is controlled by the rate of removal of HF from the system, and when this is very slow, a highly crystalline a-ZrP is obtained. The gamma form of the metal phosphate differs significantly from the alpha and current discussion will be concerned with the latter phase. 

The Phosphites.—Two series of phosphites are known, the primary phosphites, MH2POj, and the secondary, M2HP03, M being a univalent metal. Crystalline salts have also been prepared containing an excess of phosphorous acid. The phosphites of the alkali metals and ammonia are soluble, those of the alkaline earths sparingly soluble, while those of other metals are only very slightly soluble. They may be prepared by the usual methods —... 

Preparation of the Crystalline Acid.—Two compounds have been crystallised from concentrated solutions of phosphoric acid—the... 

We thought to start with the metal-free biomimetic transfer hydrogenation of a,(-)-unsaturated aldehydes as a model reaction which has been earlier discovered in our laboratory and independently in that of MacMillan et al. (Scheme 24). We have prepared a large number of ammonium salts as crystalline solids by mixing different primary and secondary amines with a chiral phosphoric acid. In particular, the ammonium salts of sterically hindered chiral phosphoric acids could catalyze... 

Cupric orthophosphate, Cu3(P04)2,8H20.—The orthophosphate is prepared by the interaction of disodium hydrogen phosphate and excess of cupric sulphate,6 or by heating an aqueous solution of ortho-phosphoric acid with cupric carbonate at 70° C.7 It is a blue, crystalline powder, almost insoluble in water. 

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