Anhydrides phosphoric

Replace the stopper and switch on the water-jet pump (very slow operation). When the entire phosphorus has reacted, disconnect the pump and dissolve the phosphorous anhydride gathered in tube 4 and U-tubes 5 and 6 in 10-20 ml of distilled water. Filter the solution through a paper filter and keep it for further experiments. 

What is the basicity of phosphorous acid Write the coordination formula of phosphorous acid. What coordination number does phosphorus exhibit in its compounds  

Properties of Phosphorous Acid. Divide the phosphorous acid solution into three parts. Neutralize the first part with soda up to a weakly acidic reaction and test it with a silver nitrate solution. What do you observe Heat the liquid with the precipitate. What occurs  

Add several drops of a dilute potassium permanganate solution to the second part of the solution. What happens Write the equations of the reactions. 

Put the third part of the phosphorous acid solution into a porcelain bowl and evaporate it first in a water bath, and then carefully heat it in a sand bath. What is observed Write the equation of the reaction. What properties of phosphorous acid are indicated by the above three reactions  

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Dehydration of the corresponding acid amides. This process usually requires phosphorus pentoxide (correctly termed phosphoric anhydride) as a dehydrating agent. 

Difluorophosphates. Difluorophosphates have limited appHcations largely because of hydrolytic instabiHty of the P03F 2 ion. The ammonium salt can be prepared from ammonium fluoride and phosphoric anhydride. 

Properties and Essential Information for S afe Handling and Use of Phosphoric Anhydride, Chemical Manufacturers Association Chemical Safety Data Sheet SD-28, Washington, D.C., 1974. 

Anhalonine and Lophophorine. Spath and Gangl showed that each of these alkaloids contains a methylenedioxy group and that the quarternary iodide prepared from dZ-anhalonine is identical with lophophorine methiodide so that lophophorine must be N-methylanhalonine. Anhalonine was synthesised from 3 4-methylenedioxy-5-methoxybenzaldehyde by condensation with nitromethane, reduction of the product to the corresponding -ethylamine, the acetyl derivative (VII) of which, on treatment with phosphoric anhydride, condensed to 6-methoxy-7 8-methylenedioxy-l-methyl-3 4-dihydrofsoquinoline, m.p. 60-2°. This, on reduction, furnished the corresponding tetrahydrofsoquinoline, which proved to be anhalonine (VIII), and on conversion to the quaternary methiodide the latter was found to be lophophorine (IX) methiodide. The possible alternative, 8-methoxy-6 7-methylenedioxy-l 2-dimethyl-l 2 3 4-tetrahydrofsoquinoline, was prepared by Freund s method and the methiodide shown not to be identical with lophophorine methiodide. 

FIGURE 3.10 (a) Electrostatic repnlsion between adjacent partial positive charges (on carbon and phosphorns, respectively) is relieved upon hydrolysis of the anhydride bonds of acetic anhydride and phosphoric anhydrides. The predominant form of pyrophosphate at pH values between 6.7 and 9.4 is shown, (b) The competing resonances of acetic anhydride and the simnltaneons resonance forms of the hydrolysis product, acetate. 

The situation with phosphoric anhydrides is similar. The phosphorus atoms of the pyrophosphate anion are electron-withdrawing and destabilize PPj with respect to its hydrolysis products. Furthermore, the reverse reaction, reformation of the anhydride bond from the two anionic products, requires that the electrostatic repulsion between these anions be overcome (see following). 

Resonance stabilization in the products is best illustrated by the reactant anhydrides (Figure 3.10b). The unpaired electrons of the bridging oxygen atoms in acetic anhydride (and phosphoric anhydride) cannot participate in resonance structures with both electrophilic centers at once. This competing resonance situation is relieved in the product acetate or phosphate molecules. 

For the phosphoric anhydrides, and for most of the high-energy compounds discussed here, there is an additional entropic contribution to the free energy of hydrolysis. Most of the hydrolysis reactions of Table 3.3 result in an increase in the number of molecules in solution. As shown in Figure 3.11, the hydrolysis of ATP (as pH values above 7) creates three species—ADP, inorganic phosphate (Pi), and a hydrogen ion—from only two reactants (ATP and HgO). The entropy of the solution increases because the more particles, the more disordered the system. (This effect is ionization-dependent because, at low pH, the... 

The concepts of destabilization of reactants and stabilization of products described for pyrophosphate also apply for ATP and other phosphoric anhydrides (Figure 3.11). ATP and ADP are destabilized relative to the hydrolysis products by electrostatic repulsion, competing resonance, and entropy. AMP, on the other hand, is a phosphate ester (not an anhydride) possessing only a single phosphoryl group and is not markedly different from the product inorganic phosphate in terms of electrostatic repulsion and resonance stabilization. Thus, the AG° for hydrolysis of AMP is much smaller than the corresponding values for ATP and ADP. 

FIGURE 11.15 Formadoii of ADP and ATP by the successive addition of phosphate groups via phosphoric anhydride linkages. Note the removal of equivalents of H9O in these dehydration synthesis reactions. 

As shown in Figure 16.10, this reaction mechanism involves nucleophilic attack by —SH on the substrate glyceraldehyde-3-P to form a covalent acylcysteine (or hemithioaeetal) intermediate. Hydride transfer to NAD generates a thioester intermediate. Nucleophilic attack by phosphate yields the desired mixed carboxylic-phosphoric anhydride product, 1,3-bisphosphoglycerate. Several examples of covalent catalysis will be discussed in detail in later chapters. 

Pantothenic acid, sometimes called vitamin B3, is a vitamin that makes up one part of a complex coenzyme called coenzyme A (CoA) (Figure 18.23). Pantothenic acid is also a constituent of acyl carrier proteins. Coenzyme A consists of 3, 5 -adenosine bisphosphate joined to 4-phosphopantetheine in a phosphoric anhydride linkage. Phosphopantetheine in turn consists of three parts /3-mercaptoethylamine linked to /3-alanine, which makes an amide bond with a branched-chain dihydroxy acid. As was the case for the nicotinamide and flavin coenzymes, the adenine nucleotide moiety of CoA acts as a recognition site, increasing the affinity and specificity of CoA binding to its enzymes. 

Phosphorigsaureanhydrid, n. phosphorous anhydride (phosphorus trioxide, phosphorus-(III) oxide). 

Phosphorsaure, /. phosphoric acid, -anhydrid, n. phosphoric anhydride (phosphorus pentoxide). -losimg, /. phosphoric acid solution, -salz, n. phosphate. 

Methoxy4,5-e2imido Benzoic Acid 1 -AI yl-2-amino-methyl Pyrrolidine Phosphoric Anhydride... 

G) 2-(n)-Propyl-lsonicotinic-Nitrile The 20 grams of the amide just obtained are treated with 32 grams of phosphoric anhydride. 11 grams of nitrile, having a BP of 90°-95°C/4 mm, are obtained. 

Acyl CoA s, such as acetyl CoA, are the most common thioesters in nature. Coenzyme A, abbreviated CoA, is a thiol formed by a phosphoric anhydride linkage (0 = P—O—P=0) between phosphopantetheine and adenosine 3, 5 -bisphosphate. (The prefix "bis" means "two" and indicates that adenosine 3, 5 -bisphosphate has two phosphate groups, one on C3 and one on C5. ) Reaction of coenzyme A with an acyl phosphate or acyl adenylate... 

Like all anhydrides (Section 21.5), the mixed carboxylic-phosphoric anhydride is a reactive substrate in nucleophilic acyl (or phosphoryl) substitution reactions. Reaction of 1,3-bisphosphoglycerate with ADR occurs in step 7 by substitution on phosphorus, resulting in transfer of a phosphate group to ADP and giving ATP plus 3-phosphoglycerate. The process is catalyzed by phospho-gjvcerate kinase and requires Mg2+ as cofactor. Together, steps 6 and 7 accomplish the oxidation of an aldehyde to a carboxylic acid. 

Phosphorus Pentoxide (Phosphoric anhydride, Phosphoric oxide, Diphosphorus pentoxide). 

The mixed sulfuric phosphoric anhydride (PAdoPS or PAPS) of 3 -phospho-5 -adenylic acid is named as an acyl sulfate ... 

Alcohols can also be acylated by mixed organic-inorganic anhydrides, such as acetic-phosphoric anhydride, MeCOOPO(OH)2 (see 10-35). ... 

Another useful reagent for amide formation is compound 1, known as BOP-C1,141 which also proceeds by formation of a mixed carboxylic phosphoric anhydride. 

Several successful cyclizations of quite complex structures were achieved using polyphosphoric acid trimethylsilyl ester, a viscous material that contains reactive anhydrides of phosphoric acid.58 Presumably the reactive acylating agent is a mixed phosphoric anhydride of the carboxylic acid. 

In all cases the reaction products are mixtures of ethyl polyphosphates, and, on the basis of elementary analysis, they approximate the empirical formulas given in the above equations. In Equations 3 and 5 the product has been arbitrarily called hexaethyl tetraphosphate, which may contain 8 to 20% of the active tetraethyl pyrophosphate. In Equations 4 and 6 the products have been called technical tetraethyl pyrophosphate, which may contain up to 40% of pure tetraethyl pyrophosphate. Hexaethyl tetra-phosphate has also been made from phosphoric anhydride and diethyl ether by a process recently patented by Adler (1). 

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