Directed metallation

Directed Oxidation of a Molten Metal. Directed oxidation of a molten metal or the Lanxide process (45,68,91) involves the reaction of a molten metal with a gaseous oxidant, eg, A1 with O2 in air, to form a porous three-dimensional oxide that grows outward from the metal/ceramic surface. The process proceeds via capillary action as the molten metal wicks into open pore channels in the oxide scale growth. Reinforced ceramic matrix composites can be formed by positioning inert filler materials, eg, fibers, whiskers, and/or particulates, in the path of the oxide scale growth. The resultant composite is comprised of both interconnected metal and ceramic. Typically 5—30 vol % metal remains after processing. The composite product maintains many of the desirable properties of a ceramic however, the presence of the metal serves to increase the fracture toughness of the composite. 

Grown Ethers. Ethylene oxide forms cycHc oligomers (crown ethers) in the presence of fluorinated Lewis acids such as boron tritiuoride, phosphoms pentafluoride, or antimony pentafluoride. Hydrogen fluoride is the preferred catalyst (47). The presence of BF , PF , or SbF salts of alkah, alkaline earth, or transition metals directs the oligomerization to the cycHc tetramer, 1,4,7,10-tetraoxacyclododecane [294-93-9] (12-crown-4), pentamer, 1,4,7,10,13-pentaoxacyclopentadecane [33100-27-6] (15-crown-6), andhexamer, 1,4,7,10,13,16-hexaoxacyclooctadecane [17455-13-9]... 

The deposition of metals directly from these halides would require high temperatures to be efficient, but because of the thermodynamic stabilities of the hydrogen halides, direct reduction can readily be carried out with hydrogen at lower temperamres. The general reaction... 

Electric arc process. Patented by Siemens in 1878, this u.ses an electric current through the metal (direct-arc), or an arc just above the metal (indirect-arc), as a means of heating. It is widely used in the manufacture of alloy- and other high-quality steels. 

Metal-directed self-assembly of two- and three-dimensional synthetic receptors (macroheterocycles involving transition metal atoms, among them chelated atoms) 98CSR417. 

Other Microorganisms. There are several other microorganisms that affect the corrosion of metal directly or indirectly. Some examples are yeasts and molds, algae and protozoa. For the present purposes it is sufficient to realize that there are other micro-... 

Second, oxygen attacks the metal directly by precipitating iron oxide at the anode, thus, preventing anodic polarization by Fe ions. 

Other Pyrochemical Processes. The chemistry of pyrochemi-cal separation processes is another fertile area of research e.g., new molten salt systems, scrub alloys, etc. and the behavior of plutonium in these systems. Studies of liquid plutonium metal processes should also be explored, such as filtration methods to remove impurities. Since Rocky Flats uses plutonium in the metal form, methods to convert plutonium compounds to metal and purify the metal directly are high-priority research projects. 

Even if microorganisms do not mediate a reaction with the metal directly, e.g., by chang-... 

P. S. Skell Reactions of atoms silicon and the high-boiling metals. Direct syntheses of organometallics, pp. 215-221 (10). 

Acceleration of the Template- and Metal-Directed Polycondensation of Nucleoside-5 -phosphoric Imidazolides by Acylation... 

It should be noted that all terms concerning the electrons in the metals as well as those connected with the metals not directly participating in the cell reaction (Pt) have disappeared from the final Eq. (3.1.49). This result is of general significance, i.e. the EMFs of cell reactions involving oxidation-reduction processes do not depend on the nature of the metals where those reactions take place. The situation is, of course, different in the case of a metal directly participating in the cell reaction (for example, silver in the above case). 

Scrap metal Direct reduced iron Hot briquetted iron Cold pig iron Hot metal... 

The macrocyclic tetraene 2,3,9,10-Me4[14]tetraene (tmt) may be synthesized by a metal-directed condensation between trimethylenediamine (tn) and 2,3-butanedione in the presence of Co(OAc)2, ultimately resulting in the trans-dichloro Co111 complex [Co(tmt)Cl2]+ (59).302... 

Architectural control of transition metal-directed assembly to construct well-arranged metallo-macrocycles is one of the current research areas to create organized nanostructures for advanced materials.510-513... 

Ans. The copperOD ions would migrate to the zinc electrode and be reduced to copper metal directly. The zinc electrode would become copper plated, and the cell would not function. 

Mechanism [4] was based on studies involving the direct reaction of antimony metal with DBDPO in the absence of a hydrogen source. The data from these experiments clearly show that if the oxide is reduced to the metal, direct interaction with DBDPO would occur, and that this is a specific and highly exothermic reaction. However, no direct evidence for the presence of metallic antimony in mixtures containing antimony oxide, a polymer substrate and an organohalogen compound was obtained. 

A few measurements are available that relate to the ion pair acidity of ethylene and some other alkenes. Ethylene is difficult to metallate directly, but vinyl bromides and iodides undergo facile transmetallation with alkyllithium reagents. Applequist and O Brien determined the equilibrium constants of transmetallation exchange reactions as a measure of relative acidity (equations 6 and 7)25. 

A rhodium-catalyzed intramolecular C-H functionalization has been employed for the synthesis of bicyclic imidazoles. The alkene acts as an anchor to the metal, directing the C-H functionalization process, which involves the formation of an Rh(l) carbene intermediate (Equation (118)).107... 

CHLOROCYCLOBUTANE, 51, 106 Mesitylene, cyanation, 50, 54 METHALATION OF 2-METHYLPYRIDINE DERIVATIVES ETHYL 6-METHYL-PYRIDINE-2-ACETATE, 52, 75 Metalation, directed, 53, 59 Methallyl alcohol, with phenyl-mercuric acetate to yield 2-methyl-3-phenylpropional-dehyde, 51, 17 METHALLYLBENZENE, 52, 115 7r-Methallylnickel bromide, 52, 115... 

---