Titanium-carbon system, oxidation

Unsaturated chiral a-hydroxy esters are of interest due to possible reactions with the carbon double bond. They can easily be obtained from optically active cyanohydrins according to the Pinner method [35a]. Epoxidation of the chiral alcohols 9 with achiral oxidants, e.g., m-chloroperoxybenzoic acid (m-CPBA), yields a mixture of both possible epoxides 10a and 10b. With chiral (Sharpless titanium tartrate system) oxidants stereoselective epoxidation results. Using (+) dimethyl tartrate [(+) DMT] only the erythro isomer 10a is obtained (Scheme 6) [35b]. 

A very detailed description of the chemistry associated with titanium oxygen systems is available [4]. The material is very thermally stable, and extremely resistant toward chemical degradation. It can be partially reduced when heated in the presence of hydrogen or carbon monoxide, the products being either lower oxides or mixtures of titanium carbide and lower oxides. Reduction by active metals (Na, K, Ca, or Mg) can... 

Uses Wetting agent and dispersant for carbon black, titanium dioxide, Iron oxide pigments, org. color pigments in nonaq. systems Features Improves color uniformity and development provides high Initial gloss ... 

We have used a rat traeheal explant system to examine the role of AOS in particle uptake. When traeheal explants are briefly immersed in a suspension of a mineral dust, dust partieles adhere to the epithelial cell surfaces if the explants are then maintained in organ eulture in air, the epithelial cells slowly take up particles from the apical surface (see Fig. 1). The relative basal level of uptake of different types of particles is quite different (see Table 3), but every type of mineral particle thus far examined (asbestos, carbon, titanium dioxide, iron oxide, talc, wollastonite, or silicon carbide) enters the epithelial cells (3,4,51-54). This system offers several simplifying advantages for studying particle uptake, ineluding lack of airspace inflammatory cells, maintenance of normal levels of intraeel-lular antioxidant defense (Churg A, unpublished data), and retention of a polarized cell structure with normal apical differentiation. 

All of these results are consistent with the notion that surface migration of titanium oxide species Is an Important factor that contributes to the suppression of carbon monoxide chemisorption. The H2 chemisorption experiments on 1-2 ML of Ft, where no migration Is observed, strongly Indicate that electronic (bonding) Interactions are also occurring. Thus, for the tltanla system, both electronic Interactions and surface site blocking due to titanium oxide species must be considered In Interpreting SMSI effects. 

The Matrix TiOa photocatalytic treatment system is a technology that destroys dissolved organic contaminants in water in a continuous-flow process at ambient temperature. The technology uses ultraviolet (UV) light and a titanium dioxide (TiOa) semiconductor catalyst to break hydroxide ions (OH ) and water (H2O) into hydroxyl radicals (OH ). The radicals oxidize the organic contaminants to form carbon dioxide, water, and halide ions (if the contaminant was halogenated). 

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