Molybdate ester

Mechanisms proposed for reactions envisage complex reaction pathways. Thus in the oxidation of methacrolein catalyzed by H3PM012O40, the chemisorption of the aldehyde precedes the redox step and is thought to occur through the acid-promoted formation of a gem-diol molybdate ester. The subsequent oxidation to methacrylic acid involves Mo(VI) undergoing reduction to Mo(V). Molecular oxygen only serves to reoxidize the reduced polyanion. 

Molybdate esters These compounds are prepared by reaction of alkanols and molybdenum sources such as ammonium molybdate and molybdenum oxides, and are believed to form mononuclear mono- and dioxo- structures, as in Reaction (4.44) [54,55], These preparations are condensation reactions and require removal of water to drive the reaction to completion. Molybdate esters, like molybdenum carboxylates, show synergistic effects with diaryl amines [52] and with combinations of diaryl amines and sulphurised hindered phenols and/or sulphurised olefins [53],... 

For formation of anticorrosive and adhesion-improving protective layers on metals the cleaned surface is treated with aqueous acidic solution containing molybdate, chromium fluoride, phosphate, acetate, and Zn ions. As dispersant a mixture of 60% alkali salt of a phosphate ester, 20% alkylpolyglucoside, and 20% fatty alcohol ethoxylate was applied. This method passivates the metal surface by formation of an anticorrosive and protective layer that improves adhesion of subsequent coatings. 

Cambella and Antia [385] determined phosphonates in seawater by fractionation of the total phosphorus. The seawater sample was divided into two aliquots. The first was analysed for total phosphorus by the nitrate oxidation method capable of breaking down phosphonates, phosphate esters, nucleotides, and polyphosphates. The second aliquot was added to a suspension of bacterial (Escherichia coli) alkaline phosphatase enzyme, incubated for 2h at 37 °C and subjected to hot acid hydrolysis for 1 h. The resultant hot acid-enzyme sample was assayed for molybdate reactive phosphate which was estimated as the sum of enzyme hydrolysable phosphate and acid hydrolysable... 

The ester group is then hydrolysed, and the hydrolysis normally stops at the MePO(OH)2 stage. More vigorous conditions are required to rupture the Me—P bond. Thus the normal hydrolysis product of D.F.P. and of tabun, namely, phosphoric acid, will give a positive test with ammonium molybdate, whereas the product from sarin, namely, methylphosphonic acid, will not respond to this test. Vigorous reagents such as hot nitric acid and ammonium persulphate will break the C—P link and then a positive test for phosphate is obtained with ammonium molybdate. Sarin can be prepared in a variety of ways. Three... 

A [3,3] sigmatropic rearrangement of an inorganic ester such as vanadate or molybdate is considered to be involved in one of the reasonable mechanisms. 

An early attempt to analyse organophosphorus compounds, specifically phosphoric esters, was made with paper chromatography250. The esters were spotted on filter-paper and developed with a variety of solvent mixtures in order to isolate the different components of the samples. The paper was dried, sprayed with an acidic molybdate solution, heated to about 85 °C in order to hydrolyse the compounds and finally immersed... 

Another type of carbohydrate complex is the cyclic ester formed between a glycitol and a polyanion such as borate or molybdate (4). The possible species present at equilibrium have not previously been evaluated by iteration. The system mannitol-borate has been so analyzed, and it was possible to use the same approach as that for the metal chelates. 

Calvin and coworkers, in their classical studies of photosynthetic processes, detected labeled triose phosphates and hexose phosphates on bi-dimensional chromatograms, using phenol-water and 1-butanol-pro-pionic acid-water as solvents.120121 In addition to the detection of radioactivity, an ammonium molybdate-nitric acid color reagent was used to detect phosphorus.16 Acidic-solvent developers were used to obviate decomposition of the esters. 

When lecithin is hydrolyzed in acidic medium, both the fatty acid ester bonds and the phosphate ester bonds are broken and free fatty acids and inorganic phosphate are released. Using a molybdate test, we can detect the presence of phosphate in the... 

---