Condensation of phosphoric acid

Phosphoms modified phenolics are synthesized by condensation of phosphoric acid esters and phosphorus oxychloride with phenolic resins or phenol in the presence of 1,4-dioxane [175-178], The formation of eight-membered cyclic ring structures by intramolecular esterification (Scheme 28) occurs if ortho-linked novolacs are used in the reaction with difimctional phosphorus oxychlorides [177],... 

A large number of inorganic polycondensation reactions are also known. However, here again, only a few reactions have become really important for example, the poly condensation of dimethyl dichlorosilanes with water (Section 33.3.2) or the self-condensation of phosphoric acid (Section 33.3.3). 

The crude acetonitrile contains as impurity chiefly acetic acid, arising from the action of phosphoric acid on the acetamide. Therefore add to the nitrile about half its volume of water, and then add powdered dry potassium carbonate until the well-shaken mixture is saturated. The potassium carbonate neutralises any acetic acid present, and at the same time salts out the otherwise water-soluble nitrile as a separate upper layer. Allow to stand for 20 minutes with further occasional shaking. Now decant the mixed liquids into a separating-funnel, run off the lower carbonate layer as completely as possible, and then pour off the acetonitrile into a 25 ml, distilling-flask into which about 3-4 g. of phosphorus pentoxide have been placed immediately before. Fit a thermometer and water-condenser to the flask and distil the acetonitrile slowly, collecting the fraction of b.p. 79-82°. Yield 9 5 g. (12 ml.). 

The condensation of cyclohexanol or cyclohexene is generally carried out in the presence of phosphoric acid, pyrophosphoric acid, or HY 2eohtes the aromatization of intermediate cyclohexyUiydroquinone [4197-75-5] (19) is realized in the presence of a dehydrogenation catalyst. 

At equihbrium, the specific composition of a concentrated phosphoric acid is a function of its P2 s content. Phosphoric acid solutions up to a concentration equivalent of about 94% H PO (68% P2O5) contain H PO as the only phosphoric acid species present. At higher concentrations, the orthophosphoric acid undergoes condensation (polymerization by dehydration) to yield a mixture of phosphoric acid species (Table 5), often referred to genericaHy as polyphosphoric or superphosphoric acid, H20/P20 = - 3, or ultraphosphoric acid, H20/P20 = - 1. At the theoretical P2O5 concentration for orthophosphoric acid of 72.4%, the solution is actually a mixture containing 13% pyrophosphoric acid and about 1% free water. Because the pyrophosphoric acid present is the result of an equihbrium state dependent on the P2 5 content of the solution, pure orthophosphoric acid can be obtained because of a shift in equihbrium back to H PO upon crystallization. 

The only clearly defined crystalline compositions are three forms of phosphoric acid and hemihydrate, pyrophosphoric acid, and crystalline P O q. The phosphoric acids obtained in highly concentrated solutions or by mixing phosphoric acid with phosphoms pentoxide are members of a continuous series of amorphous (excluding [Y OO]) condensed phosphoric acid mixtures. Mixtures having more than 86% P2O5 contain some cyclic metaphosphoric... 

Commercial condensed phosphoric acids are mixtures of linear polyphosphoric acids made by the thermal process either direcdy or as a by-product of heat recovery. Wet-process acid may also be concentrated to - 70% P2O5 by evaporation. Liaear phosphoric acids are strongly hygroscopic and undergo viscosity changes and hydrolysis to less complex forms when exposed to moist air. Upon dissolution ia excess water, hydrolytic degradation to phosphoric acid occurs the hydrolysis rate is highly temperature-dependent. At 25°C, the half-life for the formation of phosphoric acid from the condensed forms is several days, whereas at 100°C the half-life is a matter of minutes. 

The dimer of phosphonic acid, diphosphonic acid [36465-90-4] (pyrophosphoms acid), H4P2O3, is formed by the reaction of phosphoms trichloride and phosphonic acid in the ratio of 1 5. It is also formed by the thermal decomposition of phosphonic acid. Unlike the chemistry of phosphoric acid, thermal dehydration does not lead to polymers beyond the dimer extended dehydration leads to a disproportionation to condensed forms of phosphoric acid, such as [2466-09-3] and phosphine. 

Ferrocene (46.4 g., 0.250 mole) (Note 1) is added to a well-stirred solution of 43.2 g. (0.422 mole) of bis(dimethylamino)-methane (Note 2) and 43.2 g. of phosphoric acid in 400 ml. of acetic acid in a 2-1. three-necked round-bottomed flask equipped with a condenser, a nitrogen inlet, and a mechanical stirrer (Note 3). The resulting suspension is heated on a steam bath under a slow stream of nitrogen (Note 4) for 5 hours (Note 5). The reaction mixture, a dark-amber solution, is allowed to cool to room temperature and is diluted with 550 ml. of water. The unreacted ferrocene is removed by extracting the solution with three 325-ml. jiortions of ether. The aqueous solution is then looled in ice water and made alkaline by the addition of 245 g. 

Proceeding from 5 -0-acetylazauridine (80), a mixture of 2 - and 3 -monophosphates (81, 82) was prepared by phosphorylation with polyphosphoric acid, and these were converted into the 2, 3 -cyclic phosphate (83). From the 2, 3 -0-isopropylidene derivative of 3-methyl-6-azauridine the 5 -phosphate was prepared by treatment with cyanoethylphosphate and the corresponding diphosphate from its morpholidate through the action of phosphoric acid. ° Furthermore, a diribonucleoside phosphate (85) with a natural 3 -5 internucleotide linkage was prepared from 6-azauridine, The starting material for the preparation of such derivatives was 5 -0-acetyl-2 -0 -tetrahydro-pyranyluridine-3 -phosphate (84) which was condensed with di-G-acetylazauridine (86) or with 2b3 -0-isopropylidene-6-azauridine (76) with the aid of dicyclohexylcarbodiimide. ... 

Tlie condensation of nitromalonic aldehyde (26) with 2,6-diaminopyridine (27) in the presence of phosphoric acid, affording 2-amino-6-nitro-l,8-naphthyridine (28,37%) (77TL2087), is another example of a successful application of a nitro aliphatic compound in the synthesis of nitronaphthy-ridines. 

Condensed phosphates are indirectly manufactured derivatives of phosphorous acids, having less water than orthophosphoric acid (two molecules of phosphoric can be written P205 3H20, which indicates the source of the condensation reaction). Condensed phosphates are typically available in either crystalline or glassy forms. 

The ability of phosphoric acid to form condensed molecules is an additional effect. Examples of this kind of acid are pyrophosphoric acid, H4P207 structure (1), and triphosphoric acid, H5P3O 0 structure (2) ... 

There also exists interference from diphosphoric acid, other more highly condensed phosphoric acids, and their organic derivatives. The free phosphoric acid can be determined as a heteropolyacid complex of phosphoric acid and ammonium molybdate. Afterward the complex is reduced by stannum II chloride to molybdenum blue. The amount of this dye can be measured photometricly at 625 nm. Organic derivatives of phosphoric acid and condensed phosphoric acids do not interfere with this method. 

Two molecules of phosphoric acid can undergo a condensation reaction, eliminating a water molecule and forming a P—O—phosphate linkage ... 

The use of the triphenylphosphine-di(2-pyridyl) disulphide reagent for effecting condensation reactions has been reviewed.84 Combination of triphenylphosphine with bis(O-thiocarbonyl) disulphide gives a superior reagent compared to that mentioned above for the preparation of mixed diesters of phosphoric acid from monophosphate esters.86... 

Attack on Nitrogen. A variety of cyclic derivatives of phosphorous acid have been converted into spirophosphoranes (51), using diethyl azodicarboxylate as the condensing agent,42 probably by initial addition to nitrogen to give (50). Several... 

This subcategory involves sodium tripolyphosphate and calcium phosphates. Sodium tripolyphosphate is manufactured by the neutralization of phosphoric acid by soda ash or caustic soda and soda ash, with the subsequent calcining of the dried mono- and disodium phosphate crystals. This product is then slowly cooled or tempered to produce the condensed form of the phosphates. 

The shikimate pathway begins with a coupling of phosphoenolpyruvate (PEP) and D-erythrose 4-phosphate to give the seven-carbon 3-deoxy-D-arabino-heptulo-sonic acid 7-phosphate (DAHP) through an aldol-type condensation. Elimination of phosphoric acid from DAHP, followed by an intramolecular aldol reaction, generates the first carbocyclic intermediate, 3-dehydroquinic acid. Shikimic acid (394) is... 

Raspberry ketone is prepared by alkali-catalyzed condensation of the alkali salt of 4-hydroxybenzaldehyde and acetone, followed by selective hydrogenation of the double bond in the resulting 4-hydroxybenzalacetone. Other syntheses start from phenol which is converted into 4-(4-hydroxyphenyl)-2-butanone with methyl vinyl ketone (e.g., in the presence of phosphoric acid) [179] or with 4-hydroxy-2-butanone in the presence of concentrated sulfuric acid [180]. 

A mixture of 118 g. (1 mole) of succinic acid, 188 g. (2 moles) of phenol, and 138 g. (83 ml., 0.9 mole) of phosphorus oxychloride (Note 1) is placed in a 2-1. round-bottomed flask fitted with an efficient reflux condenser capped with a calcium chloride tube (Notes 2 and 3). The mixture is heated on a steam bath in a hood (Note 3) for 1.25 hours, 500 ml. of benzene is added, and the refluxing is continued for an additional hour. The hot benzene solution is decanted from the red syrupy residue of phosphoric acid and filtered by gravity into a 1-1. Erlenmeyer flask. The syrupy residue is extracted with two 100-ml. portions of hot benzene, which are also filtered into the Erlenmeyer flask. The combined benzene solutions are concentrated to a volume of about 600 ml. (Note 4), and the pale yellow solution is allowed to cool, whereupon the diphenyl succinate separates as colorless crystals. It is filtered with suction on a Buchner funnel, washed with three 50-ml. portions of ether, and dried on a porous plate at 40°. The yield of diphenyl succinate, m.p. 120-121°, is 167— 181 g. (62-67%) (Note 5). 

To 68 g. (0.5 mole) of phenylacetic acid (Org. Syn. 2, 63) (Note 1) in a i-l. flask fitted with a reflux condenser and a system for absorbing hydrogen chloride (Org. Syn. 8, 27) (Note 2), is added 35 g. (0.25 mole) of phosphorus trichloride. The mixture is heated on a steam bath for one hour. While the contents of the flask are still warm, 400 cc. of dry benzene is added. The benzene solution of phenylacetyl chloride is decanted from the residue of phosphorous acid on 75 g. (0.56 mole) of anhydrous aluminum chloride in a dry, i-l. flask which can be fitted to the same condenser. The reaction is vigorous at first and cooling is necessary. The mixture is refluxed for one hour on a steam bath, then cooled and poured into a mixture of 500 g. of cracked ice and 200 g. of concentrated hydrochloric acid. The benzene layer is separated, and the aqueous layer is extracted once with a mixture of 100 cc. of benzene and 100 cc. of ether (Note 2). The ether-benzene solution is washed once with 100 cc. of water (Note 3), and then dried over 40-50 g. of calcium chloride. The solution is filtered (Note 4) with suction into a i-l. Claiscn flask and the solvent is removed by distillation under reduced pressure (Note 5) the residue consists of a brown oil which solidifies on cooling. 

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