Hydrogen diphosphate

Prussic acid, see Hydrogen cyanide Pyrite, see Iron disulfide Pyrochroite, see Manganese(H) hydroxide Pyrohytpophosphite, see diphosphate(IV)... 

The structure and formation of ATP. (A) The chemical structure of adenosine triphosphate (ATP). "C" indicates carbon, "N" nitrogen, "O" oxygen, "H" hydrogen and "P" phosphorus. Note the negative charges on the phosphate groups (PO3 ). (B) ATP can be formed from adenosine diphosphate (ADP). 

The fact that a Lewis acid is able to accept an electron pair means that it must have either a vacant, low-energy orbital or a polar bond to hydrogen so that it can donate H+ (which has an empty7 Is orbital). Thus, the Lewis definition of acidity includes many species in addition to H+. For example, various metal cations, such as Mg2+, are Lewis acids because they accept a pair of electrons when they form a bond to a base. We ll also see in later chapters that certain metabolic reactions begin with an acid-base reaction between Mg2+ as a Lewis acid and an organic diphosphate or triphosphate ion as the Lewis base. 

Following this initial SN1 reaction, loss of the pro-R hydrogen gives geranyl diphosphate, itself an allylic diphosphate that dissociates a second time. Reaction of the geranyl carbocation with water in a second S>jl reaction, followed by loss of a proton, then yields geraniol. 

Problem 27.6 1 Studies of the conversion of mevalonate 5-phosphate to isopentenyl diphosphate have shown the following result. Which hydrogen, pro-R or pro-S, ends up cis to the methyl group, and which ends up trans ... 

The isomerization of isopentenyl diphosphate to dimethylally diphos phate is catalyzed by JPP isomerase and occurs through a carbocation pathway Protonation of the IPP double bond by a hydrogen-bonded cysteine residue ir the enzyme gives a tertiary carbocation intermediate, which is deprotonated b a glutamate residue as base to yield DMAPP. X-ray structural studies on the enzyme show that it holds the substrate in an unusually deep, well-protectec pocket to shield the highly reactive carbocation from reaction with solvent 01 other external substances. 

Methyl-l-propanol, l3C NMR spectrum of. 453 2-Methylpropene, heat of hydrogenation of. 187 Mevalonate, decarboxylation of, 1075 isopentenyl diphosphate from, 1072-1075... 

Markowitz, M.M., Rozen, P., Pero, R.W., Tobi, M. and Miller, D.G. (1988). Hydrogen peroxide induced adenosine diphosphate ribosyl transferase (ADPRT) response in patients with inflammatory bowel disease. Gut 29, 1680-1686. 

Tris(tetrabutylammonium) hydrogen pyrophosphate 1-Butanaminium, N,N,N-tributyl-, diphosphate (3 1) (10) (76947-02-9)... 

Sodium diphosphate is prepared by the following procedure. Disodium hydrogen phosphate dihydrate, Na2HP04 2H20, (7.12 g, 40 mmole) is placed in a 60-mL platinum crucible and heated in air at 400° for 12 hours (Product Merck for analysis K 6580). According to Porthault,2 this method leads to a tetrasodium diphosphate, Na4P207, the purity of which is better than 99.5%. No impurities can be found by chromatographic or potentiometric analysis. 

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