Phosphate reactions

The Zinc Phosphating Process. The zinc phosphating reaction involves acid attack on the substrate metal at microanodes and deposition of phosphate crystals at microcathodes (8). Liberation of hydrogen and the formation of phosphate sludge also occur. The equation for the dissolution of iron together with precipitation of dissolved iron as sludge in a nitrite accelerated system is as foUows ... 

Interestingly, however, the mechanisms of the two phosphate hydrolysis reactions in steps 9 and 11 are not the same. In step 9, water is the nucleophile, but in the glucose 6-phosphate reaction of step 11, a histidine residue on the enzyme attacks phosphorus, giving a phosphoryl enzyme intermediate that subsequently reacts with water. 

NOTE Higher incoming hardness ultimately results in a reduction in BW alkalinity because the various hardness and phosphate reactions consume alkalinity in the production of tricalcium phosphate and hydroxyapatite. 

Sulphonyl phosphates, reactions of 638 Sulphonyl radicals 215 cyclization of 1099 ESR spectra of 1090-1093 formation of 1094-1098 structure of 1090-1094 thermodynamic data for 1094 Sulphonyl sulphenes 196 Sulphonyl sulphoxides alkylation of 311 synthesis of 262... 

A coupled process links a spontaneous reaction with a nonspontaneous one. In this case, the negative free energy change of the acetyl phosphate reaction drives the conversion of ADP to ATP. 

The negative value of A Gjjg shows that the free energy released in the acetyl phosphate reaction is more than enough to drive the conversion of ADP to ATP. 

C14-0083. Although the ATP-ADP reaction is the principal energy shuttle in metabolic pathways, many other examples of coupled reactions exist. For example, the glutamic acid-glutamine reaction discussed in the text can couple with the acetyl phosphate reaction shown in Example 14-10. Write the balanced equation for the coupled reaction operating in the direction of overall spontaneity and calculate A G ° for the overall process. 

Chen, Y. S., J. N. Butler, and W. Stumm (1973), "Kinetic Study of Phosphate Reaction with Aluminum Oxide and Kaolinite", Environ. Sci. Technol. 7, 327-332. 

Glucose phosphate isomerase 5.3.1.9 Glucose-6-phosphate Fructose-6-phosphate Reaction with resorcinol... 

Parfitt, R.L. (1989) Phosphate reactions with natural allophane, ferrihydrite and goethite. 

The unusual amino acid, 1-aminocyclopropanecarboxylic acid, a precursor of the phytohormone ethylene, is biosynthesized in plants from S-adenosylmethionine. By using dideuterated S-adenosylmethionine, the reaction, under the influence of a pyridoxal phosphate dependent synthase, involves an inversion at the x-carbon center (a feature rarely observed for pyridoxal phosphate reactions), leading to (5)-l-amino-2,2-dideuterocyclopropanecarboxylic acid4. 

FIGURE 20-10 Third stage of C02 assimilation. This schematic diagram shows the interconversions of triose phosphates and pentose phosphates. Black dots represent the number of carbons in each compound. The starting materials are glyceraldehyde 3-phosphate and dihydroxyacetone phosphate. Reactions catalyzed by transaldolase ( and ) and transketolase ((3) and ) produce pentose phosphates that are converted to ribulose 1,5-bisphosphate—ribose... 

Formation of pyruvate. The conversion of glucose to pyruvate requires ten enzymes (Fig. 17-7), and the sequence can be divided into four stages preparation for chain cleavage (reactions 1-3), cleavage and equilibration of triose phosphates (reactions 4 and 5), oxidative generation of ATP (reactions 6 and 7), and conversion of 3-phosphoglycerate to pyruvate (reactions 8-10). 

In zinc phosphating. a small amount of iron phosphate is formed initially, bul ihe bath contains primary zinc phosphate. ZnlHiP04)>, which crystallizes on Ihe metal surface as secondary and tertiary zinc phosphates, ZnHP04 and Znt(P04 j. respectively, when the pH rises at the mclal/solulion interlace. The most frequently used baths contain accelerators, preferably nitrates and nitrites, which oxidize the hydrogen lormcd hy the pickling reactions. The fundamental zinc phosphate reactions occur in three steps, all in the same hath ... 

In Scheme 19, it is shown that the radical-cation 117 can either be attacked by the nucleophile water (reactions 182 and 183), or by the nucleophile phosphate (reactions 184 and 185) of the phosphoric ester that is still attached to the radical-cation. Because the formation of the radical-cations is fast, the phosphate-bridged radicals 120 and 121, formed in reactions 184 and 185, may be in equilibrium with 117 and with one another. They are probably unstable, and rapidly revert to 117 before they can undergo radical-radical reactions. 

The 32P-postlabeling technique allows to improve the sensitivity of the detection of DNA damage (Cadet et al. 1998). The damaged DNA is enzymatically degraded into nucleotide-3-phosphates [reaction (7)]. The resulting mixture of unchanged nucleoside-3-phosphates (dNp) and damaged ones (dXP) are separated by HPLC [reaction (8)]. They are then labeled at the 5 -position with 32P [reaction (9)] and subsequently dephosphorylated at the 3 -position [reaction (10)]. This allows to proceed with a second purification and their identification by, for example, two-dimensional TLC [reactions (11) and (12)]. 

Phosphate reactions on calcite (Kuo and Lotse, 1972 Griffin and Jurinak, 1974) have been described using second-order reactions. Also, recent work on A1 reactions in soils has employed second-order reactions (Jardine and Zelazny, 1986). 

Lin, C., Busscher, W. J., and Douglas, L. A. (1983). Multifactor kinetics of phosphate reactions with minerals in acid soils. II, Experimental curve fitting. Soil Sci. Soc. Am. J. 47, 1103-1109. 

The reaction of polybasic acids, such as phosphoric, with cellulose in the presence of an organic base such as urea (5, 8). The urea acts as a buffer in the formation of the cellulose-phosphate reaction products, reducing the weakening of die fiber. The flame resistance of this type of treatment is claimed to result from the inorganic or acid anhydride itself. 

The primaiy role of sulfur species in the tribochemical processes is passivation by sulfur species on nascent surfaces caused by a severe wear process (extreme pressure conditions) Fe2+ + S2" - FeS, the heat of formation AHf (FeS) = -1.04 eV. The sulfide can prevent adhesion and also the attack of oxygen species, AHf (FeO) = - 2.82 eV (Mori, 1995). There is enough sulfur in engine oil to initiate acid-base reactions in the formation of zinc sulfide (Martin, 1999). Organic sulfur species other than in thiophosphate form can react with the ZnO produced by the phosphate reactions according to the following ZnO + S2 - ZnS + O2. The zinc sulfide can also be directly produced if the polyphosphate contains sulfur atoms in the polymer chain (thiophosphate), for example ... 

---