Phosphoric acid hydrogen bonding

Also given in this class are two acids, phosphorous acid and hypo-phosphorous acid, which seem to be out of place, inasmuch as their formulas, H8POs and H PO, seem not to put them in this class. Their acid constants, l.fi X 10 2 and 1 X 10 2, respectively, are, however, appropriate to the class, and an explanation must be sought for the apparent abnormality. The explanation is that one of the hydrogen atoms in phosphorous acid is bonded directly to the phosphorus atom, and two of the hydrogen atoms in hypophosphorous acid are bonded... 

In anhydrous phosphoric(V) acid, tetrahedral PO4 groups are connected by hydrogen bonds, a structure which can be represented... 

Extensive hydrogen bonding takes place in phosphoric acid solutions. In concentrated (86% H PO solutions, as well as in the crystal stmctures of the anhydrous acid and the hemihydrate, the tetrahedral H PO groups are linked by hydrogen bonding. At lower (75% H PO concentrations, the tetrahedra are hydrogen-bonded to the water lattice. Physical properties of phosphoric acid solutions of various concentrations are Hsted in Table 2 the vapor pressure of aqueous H PO solutions at various temperatures is given in Table 3. 

Phosphoric acid, sulfuric acid, and the hydrogen sulfate ion are members of a group of acids known as oxoacids. An oxoacid has a central atom bonded to a variable number of oxygen atoms and OH groups. Except for the three oxoacids shown in Table (sulfuric acid, nitric acid, and perchloric acid), all of the oxoacids described in this textbook are weak acids. Chapter 17 describes in detail the chemistry of strong and weak acids, including carboxylic acids and oxoacids. 

Guidelines for the framework indicate that the phosphorus atom is in the middle, bonded to the four oxygen atoms. By recognizing the link between dihydrogen phosphate and phosphoric acid, we know that the hydrogen atoms bond to two of the oxygen atoms. 

The asymmetric hydrogenation of C=N (Eqn. (23)), in contrast with C=0 and C=C bonds, is much less developed. Hexahydrowoquinoline was used as its phosphoric acid salt. Iridium-ferrocenyl complexes were found to be sati.sfactory. After optimisiation, Meyer et al. (1997) were able to realize an enantioselectivity of 89% ee. 

Hydrogenolysis of a benzyl ether C-O bond in a phosphoric acid dimethyl ester was done in MeOH in the presence of Pd(OH)2 at room temperature under atmospheric hydrogen pressure for 12 hours (Scheme 4.36).167,168... 

Studies have indicated that the association of HF in the gas phase leads predominantly to dimers or hexamers with small amounts of tetramers. Hydrogen bonding in liquids such as sulfuric and phosphoric acids is responsible for them being viscous liquids that have high boiling points. 

Each H atoms attached to an O atom is an acidic hydrogen and can be released by the acid to a base. Phosphoric acid has 3 such H atoms and thus is triprotic. Although phosphorous acid has 3 H atoms, only 2 H atoms are bonded to an O atom, the other one is attached directly to the P atom. Thus phosphorous acid is only diprotic. A way to write this is H2PH03. 

Hydrogen bonding, 13 767. See also Hydrogen bonds in acid dyes, 9 390 in cellulose I and cellulose II, 21 6—7 in dihydroxyazo dyes, 9 395 in bquid crystalline materials, 15 105 in organic separations, 21 657-660g in phosphoric acid solutions, 18 818-819 in PVA, 25 595 in silk, 22 631... 

A novel demonstration of the latent reactivity of the phosphoryl bond and the apparent ease with which the number of ligands around the phosphorus atom can change under very mild conditions is provided by the hydrogen phosphonate (100), prepared from catechol and phosphorous acid or PC13. When treated with DCC,... 

The aim of this study is to investigate the ability of ortho-phosphoric acid to function as the pore-producing additive for the preparation of CA reverse osmosis membranes. Ortho-phosphoric acid (PA) is known to be a strongly hydrogen bonded liquid, and it has been claimed ( ) to be a promising additive for the asymmetric CA membrane formation. To our knowledge, there has not been a thorough study on the problem. 

Br0nsted acids such as thioureas 2 represent hydrogen-bonding catalysts. Phosphoric acids 3, AT-triflyl phosphoramides 4, and dicarboxyUc acids 5 are examples of stronger specific Brpnsted acids (Fig. 1). 

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