Oxide migrations

Offers better control over oxidant migration in the subsurface. 

Studies of the migration of Pu in limestones and basalts indicate that the absorption coefficients are dependent on the types and amounts of other ions present in the solution. Migration coefficients were measured for flow along the surface of fissures and through the porous stone. At least two chemical forms of Pu were present in neutral solutions and one of these, presumably a polymerized Pu oxide, migrated 10 times faster than the other form. 

Model Ni/MnOx catalysts were prepared by 150-X nickel deposition onto an oxidized manganese disk under ultra-high vacuum. The surface composition of the catalyst wa-s followed as a function of time at 500 K in ultra-high vacuum. Rapid diffusion of reduced manganese oxide onto the nickel surface was observed. This oxide migration phenomenon was observed for a wide range of metal/... 

Augustine and Sachtler, on reduction, rhenium oxides migrate over the support surface and become reduced in contact with a prereduced platinum particle. In this way, each platinum particle can generate a mixed platinum-rhenium cluster that has the beneficial effects of bimetallic catalysts on selectivity and stability. 

Moody and coworkers have observed an intriguing enhancement of diastereos-electivity for the C2 to C3 oxidative rearrangement of indole-2-carboxamides in cases where a bulky substituent was present at indole C7 [17]. Accordingly, oxidative migration of the chiral pyrrolidinamide substituent of 10 (X = H) afforded a 1.3 1 mixture of diastereomeric oxindoles 11 and 12 while similar conversions of the 7-bromo or 7-phenyl analogs of 10 afforded the corresponding oxindoles 11 and 12 in diastereomeric ratios of 8 1 and 11 1, respectively (Scheme 3). 

While participation resulting in a four-membered ring is generally rare, 0-4 participation is common in base-catalyzed reactions of appropriately substituted alcohols. For example, the epoxide (197) undergoes oxide migration to form the oxetane (198). ... 

S-Oxides, migration of carbon-carbon double bonds via -27,734... 

Five enzyme steps have been demonstrated to be required in the conversion of tyrosine to fumaric and acetoacetic acid. These consist of a transamination to p-hydroxyphenylpyruvate, a simultaneous oxidation, migration of the side chain and decarboxylation to form homogentisic acid, oxidation of the latter to maleylacetoacetic acid, isomerization of this compound to fumarylacetoacetic acid, and hydrolysis of this acid to fumaric acid and acetoacetic acid. 

A reduction in stabilizer concentration can take place in pipes as a protection mechanism against oxidation, migration, and extraction by water. The concentration profile of PE-MD pipe exposed to water internally and to air externally becomes asymmetric due to exposure. Figure 5.262 left. Maximum concentration shifts toward the pipe outer wall, because stabilizer reduction caused by extraction is higher on the inner pipe wall than reduction caused by oxidation on the outer pipe wall. If the same pipe is loaded both internally and externally by air, the concentration profile remains symmetric. Figure 5.262 right. A PB pipe exhibits a symmetric profile even under internal load by water and external load by air however, stabilizer concentration also decreases [191]. 

In order to reduce the amount of ethylene oxide migrating in the plastic and its reaction products to an acceptable level, sterilized parts are carefully degased and sometimes quarantined for several weeks prior to shipment [517]. 

Platinum oxide Migration of carbon-carbon double bonds PtO ... 

---